Azetidine and piperidine compounds useful as PDE10 inhibitors

ABSTRACT

Azetidine and piperidine compounds of formula (I): 
                         
as defined in the specification, compositions containing them, and processes for preparing such compounds and intermediates thereof. Provided herein also are methods of treating cognitive disorders or diseases treatable by inhibition of PDE10, such as Huntington&#39;s Disease, schizophrenia, bipolar disorder, obsessive-compulsive disorder, and the like.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/917,699filed Jun. 14, 2013 which claims the benefit of U.S. ProvisionalApplication No. 61/659,911, filed Jun. 14, 2012, which are herebyincorporated by reference.

FIELD OF THE INVENTION

Provided herein are novel azetidine and piperidine compounds that arePDE10 inhibitors, pharmaceutical compositions containing such compounds,and processes for preparing such compounds. Provided herein also aremethods of treating cognitive disorders or diseases treatable byinhibition of PDE10, such as Huntington's Disease, schizophrenia,bipolar disorder, obsessive-compulsive disorder, and the like.

BACKGROUND

Neurotransmitters and hormones, as well as other types of extracellularsignals such as light and odors, create intracellular signals byaltering the amounts of cyclic nucleotide monophosphates (cAMP and cGMP)within cells. These intracellular messengers alter the functions of manyintracellular proteins. Cyclic AMP regulates the activity ofcAMP-dependent protein kinase (PKA). PKA phosphorylates and regulatesthe function of many types of proteins, including ion channels, enzymes,and transcription factors. Downstream mediators of cGMP signaling alsoinclude kinases and ion channels. In addition to actions mediated bykinases, cAMP and cGMP bind directly to some cell proteins and directlyregulate their activities.

Cyclic nucleotides are produced from the actions of adenylyl cyclase andguanylyl cyclase, which convert ATP to cAMP and GTP to cGMP.Extracellular signals, often through the actions of G protein-coupledreceptors, regulate the activities of the cyclases. Alternatively, theamount of cAMP and cGMP may be altered by regulating the activities ofthe enzymes that degrade cyclic nucleotides. Cell homeostasis ismaintained by the rapid degradation of cyclic nucleotides afterstimulus-induced increases. The enzymes that degrade cyclic nucleotidesare called 3′,5′-cyclic nucleotide-specific phosphodiesterases (PDEs).

Eleven PDE gene families (PDE1-PDE11) have been identified based ontheir distinct amino acid sequences, catalytic and regulatorycharacteristics, and sensitivity to small molecule inhibitors. Thesefamilies are coded for by 21 genes; and further multiple splice variantsare transcribed from many of these genes. Expression patterns of each ofthe gene families are distinct. PDEs differ with respect to theiraffinity for cAMP and cGMP. Activities of different PDEs are regulatedby different signals. For example, PDE1 is stimulated byCa²⁺/calmodulin. PDE2 activity is stimulated by cGMP. PDE3 is inhibitedby cGMP. PDE4 is cAMP specific and is specifically inhibited byrolipram. PDE5is cGMP-specific. PDE6 is expressed in retina.

PDE10 sequences were identified by using bioinformatics and sequenceinformation from other PDE gene families (Fujishige et al., J. Biol.Chem. 274:18438-18445, 1999; Loughney et al., Gene 234:109-117, 1999;Soderling et al., Proc. Natl. Acad. Sci. USA 96:7071-7076, 1999). ThePDE10 gene family is distinguished based on its amino acid sequence,functional properties and tissue distribution. The human PDE10 gene islarge, over 200 kilobases, with up to 24 exons coding for each of thesplice variants. The amino acid sequence is characterized by two GAFdomains (which bind cGMP), a catalytic region, and alternatively splicedN and C termini. Numerous splice variants are possible because at leastthree alternative exons encode N termini and two exons encode C-termini.PDE10A1 is a 779 amino acid protein that hydrolyzes both cAMP and cGMP.The K_(m) values for cAMP and cGMP are 0.05 and 3.0 micromolar,respectively. In addition to human variants, several variants with highhomology have been isolated from both rat and mouse tissues and sequencebanks.

PDE10 RNA transcripts were initially detected in human testis and brain.Subsequent immunohistochemical analysis revealed that the highest levelsof PDE10 are expressed in the basal ganglia. Specifically, striatalneurons in the olfactory tubercle, caudate nucleus and nucleus accumbensare enriched in PDE10. Western blots did not reveal the expression ofPDE10 in other brain tissues, although immunoprecipitation of the PDE10complex was possible in hippocampal and cortical tissues. This suggeststhat the expression level of PDE10 in these other tissues is 100-foldless than in striatal neurons. Expression in hippocampus is limited tothe cell bodies, whereas PDE10 is expressed in terminals, dendrites andaxons of striatal neurons.

The tissue distribution of PDE10 indicates that PDE10 inhibitors can beused to raise levels of cAMP and/or cGMP within cells that express thePDE10 enzyme, for example, in neurons that comprise the basal gangliaand therefore would be useful in treating a variety of neuropsychiatricconditions involving the basal ganglia such as obesity, non-insulindependent diabetes, schizophrenia, bipolar disorder, obsessivecompulsive disorder, and the like.

Noninvasive, nuclear imaging techniques can be used to obtain basic anddiagnostic information about the physiology and biochemistry of avariety of living subjects including experimental animals, normal humansand patients. These techniques rely on the use of sophisticated imaginginstrumentation that is capable of detecting radiation emitted fromradiotracers administered to such living subjects. The informationobtained can be reconstructed to provide planar and tomographic imagesthat reveal distribution of the radiotracer as a function of time. Useof appropriately designed radiotracers can result in images whichcontain information on the structure, function and most importantly, thephysiology and biochemistry of the subject. Much of this informationcannot be obtained by other means. The radiotracers used in thesestudies are designed to have defined behaviors in vivo which permit thedetermination of specific information concerning the physiology orbiochemistry of the subject or the effects that various diseases ordrugs have on the physiology or biochemistry of the subject. Currently,radiotracers are available for obtaining useful information concerningsuch things as cardiac function, myocardial blood flow, lung perfusion,liver function, brain blood flow, regional brain glucose and oxygenmetabolism.

Compounds of the invention can be labeled with either positron or gammaemitting radionuclides. For imaging, the most commonly used positronemitting (PET) radionuclides are ¹¹C, ¹⁸F, ¹⁵O, ¹³N, ⁷⁶Br, ⁷⁷Br, ¹²³I,or ¹²⁵I, wherein ¹¹C, ¹⁸F, ¹²³I, or ¹²⁵ I are preferred, all of whichare accelerator produced. In the two decades, one of the most activeareas of nuclear medicine research has been the development of receptorimaging radiotracers. These tracers bind with high affinity andspecificity to selective receptors and neuroreceptors. For example,Johnson and Johnson has synthesized and evaluated ¹⁸F-JNJ41510417 as aselective and high-affinity radioligand for in vivo brain imaging ofPDE10A using PET (The Journal Of Nuclear Medicine; Vol. 51; No. 10;October 2010).

The present inventors have made an extensive study for the purpose ofdeveloping compounds for treating cognitive disorder, preferablyschizophrenia, which would be not only effective for improving thenegative symptoms, but also effective for improving the positivesymptoms of schizophrenia, furthermore such compounds would have lessside-effects as compared with those shown by drugs known in prior art.As the result, the present inventors have successfully found novelazetidine and piperidine compounds having strong and selectiveinhibition activity against PDE10 receptors. Alternatively, it is alsopreferable that the novel azetidine and piperidine compounds can bedeveloped for treating Huntington's Disease.

Azetidine and piperidine compounds disclosed in WO2011/143365 havesubstituents different from those of the azetidine and piperidinecompounds of the present invention.

Neuroscience is a particularly challenging field in drug development.Complexities in molecular signaling and electrical circuitry make itdifficult to understand disease and design treatment and the blood-brainbarrier stands in the way of therapies. The brain is arguably our mostvital organ, and is extremely sensitive to chemicals in its environment.The blood-brain barrier (BBB) protects the brain from damage by keepingmany foreign and natural molecules from entering. It surrounds all bloodvessels that feed the brain. It is composed of a single layer of cells,tightly bound together. It is not sufficient for a potentialneurotherapeutic agent to move across the BBB, it also has to stay inthe brain long enough to exert its desired action. This means that italso has to avoid being a substrate for a variety of transport proteinsthat work to extrude compounds from the brain. There are at least sixsuch outwardly directed active efflux mechanisms in the BBB (Alavijeh etal. NeuroRx. 2005 October; 2(4): 554-571, see p. 565, FIG. 3), the mostprominent of which is a phosphorylated glycoprotein calledP-glycoprotein (P-gp), a 170-kDa member of the ATP-binding cassette(ABC) superfamily of membrane transporters, which in humans is encodedby multidrug resistance gene 1 (MDR1). P-gp is located on the apicalsurface of the endothelial cells of the brain capillaries toward thevascular lumen and contributes to the poor BBB penetration of a numberof drugs. In a study of the concentration of 32 structurally diverse CNSdrugs in brain, plasma, and CSF of wild-type and (P-gp) knockout mice,29 of these drugs showed marked differences in brain/plasma ratiosbetween knockout and wild-type mice. There have been attempts toestablish quantitative structure-activity relationship (QSAR) for P-gp,but the task is made difficult by the broad specificity of thistransporter.

Under these circumstances, development of drugs for treating cognitivedisorders, such as schizophrenia, having improved Central Nervous System(CNS) drug profile such as high permeability, low efflux, high receptoror target occupancy, and high PDE10 selectivity profile have beeneagerly needed.

SUMMARY OF THE INVENTION

The present invention comprises a novel azetidine and piperidinecompounds having improved CNS drug profile useful in the treatment ofcognitive diseases, such as PDE10-mediated diseases and other maladies,such as schizophrenia, Huntington's Disease, bipolar disorder, orobsessive-compulsive disorder. Accordingly, the invention also comprisespharmaceutical compositions comprising the compounds, methods for thetreatment of PDE10-mediated cognitive diseases and other maladies, suchas schizophrenia, Huntington's Disease, bipolar disorder, orobsessive-compulsive disorder, using the compounds and compositions ofthe invention, and intermediates and processes useful for thepreparation of the compounds of the invention.

Another aspect of the invention comprises novel azetidine and piperidinecompounds radiolabeled with a positron emitting radionuclide selectedfrom ¹¹C, ¹⁸F, ¹⁵O, ¹³N, ⁷⁶Br, ⁷⁷Br, ¹²³I, or ¹²⁵I, aradiopharmaceutical composition comprising the radiolabelled compound, amethod for the diagnostic imaging of PDE10 receptors in a mammal,including human, or tissues bearing PDE10 receptors in a mammal,including human brain, which comprises administering to a mammal in needof such diagnostic imaging an effective amount of the radiolabeledcompound, and a method for the detection or quantification of PDE10enzyme in mammalian tissue, including human tissue, which comprisescontacting such mammalian tissue in which such detection orquantification is desired with an effective amount of the radiolabeledcompound.

The compounds of the invention are represented by the following generalstructure:

or a pharmaceutically acceptable salt thereof, wherein p, q, R¹, R², R³,X¹ and X² are defined below.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the current invention relates to compounds having thegeneral structure of formula (I):

or a pharmaceutically acceptable salt thereof, wherein:

X¹ is N or CR⁴;

X² is N or CR⁵;

wherein 0 to 1 of X¹ and X² are N;

each of p and q is independently 1 or 2; wherein the sum of p and q is 2or 4;

and each R¹, R², R³, R⁴, and R⁵ is independently hydrogen or halo.

In one embodiment, X¹ is N and X² is CH.

In another embodiment, X¹ is CH and X² is N.

In another embodiment, X¹ is CH and X² is CH.

In another embodiment, the sum of p and q is 4.

In another embodiment, the sum of p and q is 2.

In another embodiment, R² is fluoro.

In another embodiment, one of R¹, R², and R³ is hydrogen.

In another embodiment, two of R¹, R², and R³ are hydrogen.

In another embodiment, R¹, R², and R³ are hydrogen.

In another embodiment, one of R¹ and R² is fluoro.

In another embodiment, one of R¹ and R² is chloro.

In another embodiment, R¹ is chloro and R² is fluoro.

In another embodiment, R¹ is fluoro or chloro.

In another embodiment, R¹ is hydrogen and R² is chloro or fluoro.

In another embodiment, R¹ is chloro or fluoro and R² is hydrogen.

Another aspect of the invention relates to a compound, or apharmaceutically acceptable salt thereof, which is tabulated below: (Ex.No. stands for Example No.)

Ex. No. Structure Name 1

4-(3-(1-(7-chloro-2- quinolinyl)-4- piperidinyl)-2- pyrazinyl)-2-fluoro-N-methylbenzamide 2

2-fluoro-4-(3-(1-(7- fluoroquinolin-2- yl)piperidin-4- yl)pyrazin-2-yl)-N-methylbenzamide 3

2-fluoro-N-methyl-4-(3- (1-(2-quinolinyl)-4- piperidinyl)-2-pyrazinyl)benzamide 4

2-fluoro-4-(3-(1-(6- fluoro-2-quinolinyl)- 4-piperidinyl)-2-pyrazinyl)-N- methylbenzamide 5

2-fluoro-4-(3-(1-(8- fluoro-2-quinolinyl)- 4-piperidinyl)-2-pyrazinyl)-N- methylbenzamide 6

2-fluoro-N-methyl-4-(3-(1-(2-quinazolinyl)- 3-azetidinyl)-2-pyrazinyl)benzamide 7

2-fluoro-N-methyl-4-(3-(1-(2-quinolinyl)- 3-azetidinyl)-2-pyrazinyl)benzamide 8

2-fluoro-4-(3-(1-(7- fluoroquinolin-2- yl)azetidin-3-yl)pyrazin-2-yl)-N- methylbenzamide 9

2-fluoro-4-(3-(1-(7- fluoro-2- quinazolinyl)-3-azetidinyl)-2-pyrazinyl)-N- methylbenzamide 10

4-(3-(1-(7-chloro-2- quinazolinyl)-3- azetidinyl)-2-pyrazinyl)-2-fluoro-N- methylbenzamide 11

2-fluoro-4-(3-(1-(6- fluoro-2- quinazolinyl)-3-azetidinyl)-2-pyrazinyl)-N- methylbenzamide 12

4-(3-(1-(7-chloro-6- fluoro-2- quinazolinyl)-3-azetidinyl)-2-pyrazinyl)- 2-fluoro-N- methylbenzamide 13

2-fluoro-4-(3-(1-(6- fluoro-2-quinolinyl)- 3-azetidinyl)-2-pyrazinyl)-N-methylbenzamide 14

4-(3-(1-(7-chloro- 1,5-naphthyridin- 2-yl)-3-azetidinyl)- 2-pyrazinyl)-2-fluoro-N- methylbenzamide

Another aspect of the invention relates to a pharmaceutical compositioncomprising any one of the above compounds, or a pharmaceuticallyacceptable salt thereof, and a pharmaceutically-acceptable excipient.

Another aspect of the invention relates to a method of treatingcognitive disorder or conditions that may be treated with PDE10inhibitors comprising the step of administering to a patient in needthereof a therapeutically effective amount of any one of the abovecompounds, or a pharmaceutically acceptable salt thereof.

In one embodiment of the method, said conditions is psychoses,Parkinson's disease, dementias, obsessive compulsive disorder, tardivedyskinesia, choreas, depression, mood disorders, impulsivity, drugaddiction, attention deficit/hyperactivity disorder (ADHD), depressionwith parkinsonian states, personality changes with caudate or putamendisease, dementia and mania with caudate and pallidal diseases, orcompulsions with pallidal disease.

In another embodiment of the method, said condition is schizophrenia,Huntington's Disease, bipolar disorder, or obsessive-compulsivedisorder.

In another embodiment of the method, said condition is schizophrenia.

Another aspect of the invention relates to the use of any one of theabove compounds, or a pharmaceutically acceptable salt thereof, as amedicament.

Another aspect of the invention relates to the use of any one of theabove compounds, or a pharmaceutically acceptable salt thereof in themanufacture of a medicament for the treatment of schizophrenia,Huntington's Disease, bipolar disorder, or obsessive-compulsivedisorder.

Another aspect of the invention relates to a method of preparing acompound Formula (I), as defined above; comprising the step of:

(a) reacting a compound of formula 3 with a compound of formula 5:

wherein X¹, X², R¹, R², R³, p and q are as defined in the compound offormula (I); andwherein LG₁ is a leaving group and M is a metal moeity; in the presenceof a solvent and a catalyst; or

(b) reacting a compound of formula 2 with a compound of formula 4:

wherein X¹, X², R¹, R², R³, p and q are as defined in the compound offormula (I), and LG₂ is a leaving group; in the presence of a solventand a base; to prepare the compound of formula (I).

Another aspect of the invention relates to a compound, or apharmaceutically acceptable salt thereof, of formula:

wherein each of p and q is independently 1 or 2; and wherein the sum ofp and q is 2 or 4. In one embodiment, the sum of p and q is 4. Inanother embodiment, the sum of p and q is 2.

Another aspect of the invention relates to a compound, or apharmaceutically acceptable salt thereof, of formula:

wherein

X¹ is N or CR⁴;

X² is N or CR⁵;

wherein 0 to 1 of X¹ and X² are N;

each of p and q is independently 1 or 2; wherein the sum of p and q is 2or 4;

each R¹, R², R³, R⁴, and R⁵ is independently hydrogen or halo; and LG₁is a leaving group, such as halo.

In one embodiment of compound of formula (5), the sum of p and q is 4.

In another embodiment of compound of formula (5), the sum of p and q is2.

Yet another aspect of the current invention relates to any compound ofthe present invention, or a pharmaceutically-acceptable salt thereof,radiolabeled with a positron emitting radionuclide selected from ¹¹C,¹⁸F, ¹⁵O, ¹³N, ⁷⁶Br, ⁷⁷Br, ¹²³I or ¹²⁵I.

Yet another aspect of the current invention relates to aradiopharmaceutical composition comprising any compound of the presentinvention, or a pharmaceutically-acceptable salt thereof, radiolabeledwith a positron emitting radionuclide selected from ¹¹C, ¹⁸F, ¹⁵O, ¹³N,⁷⁶Br, ⁷⁷Br, ¹²³I, or ¹²⁵I, and at least one pharmaceutically acceptablecarrier or excipient.

Yet another aspect of the current invention relates to a method for thediagnostic imaging of PDE10 receptors in a mammal, including human, ortissues bearing PDE10 receptors in a mammal, including human brain,which comprises administering to a mammal in need of such diagnosticimaging an effective amount of any any compound of the presentinvention, or a pharmaceutically-acceptable salt thereof, radiolabeledwith a positron emitting radionuclide selected from ¹¹C, ¹⁸F, ¹⁵O, ¹³N,⁷⁶Br, ⁷⁷Br, ¹²³I, or ¹²⁵I.

Yet another aspect of the current invention relates to a method for thedetection or quantification of PDE10 receptors in mammalian tissue,including human tissue, which comprises contacting such mammalian tissuein which such detection or quantification is desired with an effectiveamount of any compound of the present invention, or apharmaceutically-acceptable salt thereof, radiolabeled with a positronemitting radionuclide selected from ¹¹C, ¹⁸F, ¹⁵O, ¹³N, ⁷⁶Br, ⁷⁷Br,¹²³I, or ¹²⁵I.

Yet another aspect of the invention relates to PET tracers such as thepresent radiolabeled PDE 10 inhibitors and currently available PETtechnology can be used, but is not limited to, to obtain the followinginformation: relationship between level of receptor or target occupancyby candidate PDE 10 inhibitors and clinical efficacy in patients; doseselection for clinical trials of PDE10 inhibitors prior to initiation oflong term clinical studies; comparative potencies of structurally novelPDE10 inhibitors; investigating the influence of PDE10 inhibitors on invivo transporter affinity and density during the treatment of clinicaltargets with PDE10 inhibitors and other agents; changes in the densityand distribution of PDE10, for example, 1) during the active stage of apsychiatric disease or condition, 2) for the evaluation of efficacyduring treatment, or 3) during remission; changes in PDE10 expressionand distribution in CNS disorders; imaging neurodegenerative diseasewhen PDE10 is upregulated; imaging neurodegenerative disease when PDE10is involved; and the like.

The present invention includes all pharmaceutically acceptableisotopically-labelled compounds of the present invention wherein one ormore atoms are replaced by atoms having the same atomic number, but anatomic mass or mass number different from the atomic mass or mass numberwhich predominates in nature.

Examples of isotopes suitable for inclusion in the compounds of theinvention include, but are not limited to, isotopes of hydrogen, such as²H and ³H, carbon, such as ¹¹C, ¹³C and ¹⁴C, chlorine, such as ³⁸Cl,fluorine, such as ¹⁸F, iodine, such as ¹²³I and ¹²⁵I, nitrogen, such as¹³N and ¹⁵N, oxygen, such as ¹⁵O, ¹⁷O and ¹⁸O, phosphorus, such as ³²P,and sulphur, such as ³⁵S.

Certain isotopically-labelled compounds of the present invention, forexample, those incorporating a radioactive isotope, are useful in drugand/or substrate tissue distribution studies. The radioactive isotopestritium, i.e. ³H, and carbon-14, i.e. ¹⁴C, are particularly useful forthis purpose in view of their ease of incorporation and ready means ofdetection.

Substitution with heavier isotopes such as deuterium, i.e. ²H, mayafford certain therapeutic advantages resulting from greater metabolicstability, for example, increased in vivo half-life or reduced dosagerequirements, and hence may be preferred in some circumstances.

Substitution with positron emitting isotopes, such as ¹¹C, ¹⁸F, ¹⁵O and¹³N, can be useful in Positron Emission Topography (PET) studies forexamining substrate receptor or target occupancy.

Isotopically-labeled compounds of the present invention can generally beprepared by conventional techniques known to those skilled in the art orby processes analogous to those described in the accompanying Examplesand Preparations using an appropriate isotopically-labeled reagent inplace of the non-labeled reagent previously employed.

Pharmaceutically acceptable solvates in accordance with the inventioninclude those wherein the solvent of crystallization may be isotopicallysubstituted, e.g. D₂O, d₆-acetone, d₆-DMSO.

Specific embodiments of the present invention include the compoundsexemplified in the Examples below and their pharmaceutically acceptablesalts, complexes, solvates, polymorphs, stereoisomers, metabolites,prodrugs, and other derivatives thereof, Unless otherwise specified, thefollowing definitions apply to terms found in the specification andclaims:

The term “C_(α-β)alkyl” means an alkyl group comprising a minimum of αand a maximum of β carbon atoms in a branched, cyclical or linearrelationship or any combination of the three, wherein α and β representintegers. The alkyl groups described in this section may also containone or two double or triple bonds. A designation of C₀alkyl indicates adirect bond. Examples of C₁₋₆alkyl include, but are not limited to thefollowing:

The term “halo” or “halogen” means a halogen atoms selected from F, Cl,Br or I.

The term “pharmaceutically acceptable salt” means a salt prepared byconventional means, and are well known by those skilled in the art. The“pharmacologically acceptable salts” include basic salts of inorganicand organic acids, including but not limited to hydrochloric acid,hydrobromic acid, sulfuric acid, phosphoric acid, methanesulfonic acid,ethanesulfonic acid, malic acid, acetic acid, oxalic acid, tartaricacid, citric acid, lactic acid, fumaric acid, succinic acid, maleicacid, salicylic acid, benzoic acid, phenylacetic acid, mandelic acid andthe like. For additional examples of “pharmacologically acceptablesalts,” and Berge et al., J. Pharm. Sci. 66:1 (1977).

The term “substituted” means that a hydrogen atom on a molecule or groupis replaced with a group or atom. Typical substitutents include:halogen, C₁₋₈alkyl, hydroxyl, C₁₋₈alkoxy, —NR^(x)R^(x), nitro, cyano,halo or perhaloC₁₋₈alkyl, C₂₋₈alkenyl, C₂₋₈alkynyl, —SR^(x),—S(═O)₂R^(x), —C(═O)OR^(x), —C(═O)R^(x), wherein each R^(x) isindependently hydrogen or C₁-C₈ alkyl. It is noted that when thesubstituent is —NR^(x)R^(x), the R^(x) groups may be joined togetherwith the nitrogen atom to form a ring.

A group or atom that replaces a hydrogen atom is also called asubstituent.

Any particular molecule or group can have one or more substituentdepending on the number of hydrogen atoms that can be replaced.

The symbol “—” represents a covalent bond and can also be used in aradical group to indicate the point of attachment to another group. Inchemical structures, the symbol is commonly used to represent a methylgroup in a molecule.

The term “leaving group” generally refers to groups readily displaceableby a nucleophile, such as an amine, a thiol or an alcohol nucleophile,or by metallic agent such as boronic acids or boronates under transitionmetal catalyzed coupling conditions. Such leaving groups are well knownin the art. Examples of such leaving groups include, but are not limitedto, N-hydroxysuccinimide, N-hydroxybenzotriazole, halides, triflates,tosylates and the like. Preferred leaving groups are indicated hereinwhere appropriate.

The term “protecting group” generally refers to groups well known in theart which are used to prevent selected reactive groups, such as carboxy,amino, hydroxy, mercapto and the like, from undergoing undesiredreactions, such as nucleophilic, electrophilic, oxidation, reduction andthe like. Preferred protecting groups are indicated herein whereappropriate. Examples of amino protecting groups include, but are notlimited to, aralkyl, substituted aralkyl, cycloalkenylalkyl andsubstituted cycloalkenyl alkyl, allyl, substituted allyl, acyl,alkoxycarbonyl, aralkoxycarbonyl, silyl and the like. Examples ofaralkyl include, but are not limited to, benzyl, ortho-methylbenzyl,trityl and benzhydryl, which can be optionally substituted with halogen,alkyl, alkoxy, hydroxy, nitro, acylamino, acyl and the like, and salts,such as phosphonium and ammonium salts. Examples of aryl groups includephenyl, naphthyl, indanyl, anthracenyl, 9-(9-phenylfluorenyl),phenanthrenyl, durenyl and the like. Examples of cycloalkenylalkyl orsubstituted cycloalkylenylalkyl radicals, preferably have 6-10 carbonatoms, include, but are not limited to, cyclohexenyl methyl and thelike. Suitable acyl, alkoxycarbonyl and aralkoxycarbonyl groups includebenzyloxycarbonyl, t-butoxycarbonyl, iso-butoxycarbonyl, benzoyl,substituted benzoyl, butyryl, acetyl, trifluoroacetyl, trichloro acetyl,phthaloyl and the like. A mixture of protecting groups can be used toprotect the same amino group, such as a primary amino group can beprotected by both an aralkyl group and an aralkoxycarbonyl group. Aminoprotecting groups can also form a heterocyclic ring with the nitrogen towhich they are attached, for example, 1,2-bis(methylene)benzene,phthalimidyl, succinimidyl, maleimidyl and the like and where theseheterocyclic groups can further include adjoining aryl and cycloalkylrings. In addition, the heterocyclic groups can be mono-, di- ortri-substituted, such as nitrophthalimidyl. Amino groups may also beprotected against undesired reactions, such as oxidation, through theformation of an addition salt, such as hydrochloride, toluenesulfonicacid, trifluoroacetic acid and the like. Many of the amino protectinggroups are also suitable for protecting carboxy, hydroxy and mercaptogroups. For example, aralkyl groups. Alkyl groups are also suitablegroups for protecting hydroxy and mercapto groups, such as tert-butyl.

Protecting groups are removed under conditions which will not affect theremaining portion of the molecule. These methods are well known in theart and include acid hydrolysis, hydrogenolysis and the like. Apreferred method involves removal of a protecting group, such as removalof a benzyloxycarbonyl group by hydrogenolysis utilizing palladium oncarbon in a suitable solvent system such as an alcohol, acetic acid, andthe like or mixtures thereof. A t-butoxycarbonyl protecting group can beremoved utilizing an inorganic or organic acid, such as HCl ortrifluoroacetic acid, in a suitable solvent system, such as dioxane ormethylene chloride. The resulting amino salt can readily be neutralizedto yield the free amine. Carboxy protecting group, such as methyl,ethyl, benzyl, tert-butyl, 4-methoxyphenylmethyl and the like, can beremoved under hydrolysis and hydrogenolysis conditions well known tothose skilled in the art.

It should be noted that compounds of the invention may contain groupsthat may exist in tautomeric forms, such as cyclic and acyclic amidineand guanidine groups, heteroatom substituted aromatic heterocyclylgroups (Y′═O, S, NR), and the like, which are illustrated in thefollowing examples:

and though one form is named, described, displayed and/or claimedherein, all the tautomeric forms are intended to be inherently includedin such name, description, display and/or claim.

Prodrugs of the compounds of this invention are also contemplated bythis invention. A prodrug is an active or inactive compound that ismodified chemically through in vivo physiological action, such ashydrolysis, metabolism and the like, into a compound of this inventionfollowing administration of the prodrug to a patient. The suitabilityand techniques involved in making and using prodrugs are well known bythose skilled in the art. For a general discussion of prodrugs involvingesters see Svensson and Tunek Drug Metabolism Reviews 165 (1988) andBundgaard Design of Prodrugs, Elsevier (1985). Examples of a maskedcarboxylate anion include a variety of esters, such as alkyl (forexample, methyl, ethyl), cycloalkyl (for example, cyclohexyl), aralkyl(for example, benzyl, p-methoxybenzyl), and alkylcarbonyloxyalkyl (forexample, pivaloyloxymethyl). Amines have been masked asarylcarbonyloxymethyl substituted derivatives which are cleaved byesterases in vivo releasing the free drug and formaldehyde (Bungaard J.Med. Chem. 2503 (1989)). Also, drugs containing an acidic NH group, suchas imidazole, imide, indole and the like, have been masked withN-acyloxymethyl groups (Bundgaard Design of Prodrugs, Elsevier (1985)).Hydroxy groups have been masked as esters and ethers. EP 039,051 (Sloanand Little, Apr. 11, 1981) discloses Mannich-base hydroxamic acidprodrugs, their preparation and use.

The term “therapeutically effective amount” means an amount of acompound that ameliorates, attenuates or eliminates one or more symptomof a particular disease or condition, or prevents or delays the onset ofone of more symptom of a particular disease or condition.

The term “patient” means animals, such as dogs, cats, cows, horses,sheep and humans. Particular patients are mammals. The term patientincludes males and females.

The term “pharmaceutically acceptable” means that the referencedsubstance, such as a compound of Formula I, or a salt of a compound ofFormula I, or a formulation containing a compound of Formula I, or aparticular excipient, are suitable for administration to a patient.

The terms “treating”, “treat” or “treatment” and the like includepreventative (e.g., prophylactic) and palliative treatment.

The term “excipient” means any pharmaceutically acceptable additive,carrier, diluent, adjuvant, or other ingredient, other than the activepharmaceutical ingredient (API), which is typically included forformulation and/or administration to a patient.

Utility and Methods of Use

Provided herein are methods for treating a cognitive disorder or diseaseby inhibiting PDE10 enzyme. The methods, in general, comprises the stepof administering a therapeutically effective amount of a compounds ofthe present invention, or an individual stereoisomer, a mixture ofstereoisomers, or a pharmaceutically acceptable salt or solvate thereof,to a patient in need thereof to treat the cognitive disorder or disease.

In certain embodiments, this invention provides a use of a compound asdescribed herein in the manufacture of a medicament for treating acognitive disorder or disease treatable by inhibition of PDE10.

The compounds of the present invention inhibit PDE10 enzyme activity,and hence raise the levels of cAMP or cGMP within cells that expressPDE10. Accordingly, inhibition of PDE10 enzyme activity would be usefulin the treatment of diseases caused by deficient amounts of cAMP or cGMPin cells. PDE10 inhibitors would also be of benefit in cases whereinraising the amount of cAMP or cGMP above normal levels results in atherapeutic effect. Inhibitors of PDE10 may be used to treat disordersof the peripheral and central nervous system, cardiovascular diseases,cancer, gastro-enterological diseases, endocrinological diseases andurological diseases.

Indications that may be treated with PDE10 inhibitors, either alone orin combination with other drugs, include, but are not limited to, thosediseases thought to be mediated in part by the basal ganglia, prefrontalcortex, and hippocampus. These indications include psychoses,Parkinson's disease, dementias, obsessive compulsive disorder, tardivedyskinesia, choreas, depression, mood disorders, impulsivity, drugaddiction, attention deficit/hyperactivity disorder (ADHD), depressionwith parkinsonian states, personality changes with caudate or putamendisease, dementia and mania with caudate and pallidal diseases, andcompulsions with pallidal disease.

Psychoses are disorders that affect an individual's perception ofreality. Psychoses are characterized by delusions and hallucinations.The compounds of the present invention are suitable for use in treatingpatients suffering from all forms of psychoses, including, but notlimited to, schizophrenia, late-onset schizophrenia, schizoaffectivedisorders, prodromal schizophrenia, and bipolar disorders. Treatment canbe for the positive symptoms of schizophrenia as well as for thecognitive deficits and negative symptoms. Other indications for PDE10inhibitors include psychoses resulting from drug abuse (includingamphetamines and PCP), encephalitis, alcoholism, epilepsy, Lupus,sarcoidosis, brain tumors, multiple sclerosis, dementia with Lewybodies, or hypoglycemia. Other psychiatric disorders, like posttraumaticstress disorder (PTSD), and schizoid personality can also be treatedwith PDE10 inhibitors.

Obsessive-compulsive disorder (OCD) has been linked to deficits in thefrontal-striatal neuronal pathways (Saxena et al., Br. J. PsychiatrySuppl, 35:26-37, 1998). Neurons in these pathways project to striatalneurons that express PDE10. PDE10 inhibitors cause cAMP to be elevatedin these neurons; elevations in cAMP result in an increase in CREBphosphorylation and thereby improve the functional state of theseneurons. The compounds of the present invention are therefore suitablefor use in the indication of OCD. OCD may result, in some cases, fromstreptococcal infections that cause autoimmune reactions in the basalganglia (Giedd et al., Am J Psychiatry. 157:281-283, 2000). BecausePDE10 inhibitors may serve a neuroprotective role, administration ofPDE10 inhibitors may prevent the damage to the basal ganglia afterrepeated streptococcal infections and thereby prevent the development ofOCD.

In the brain, the level of cAMP or cGMP within neurons is believed to berelated to the quality of memory, especially long term memory. Withoutwishing to be bound to any particular mechanism, it is proposed that,since PDE10 degrades cAMP or cGMP, the level of this enzyme affectsmemory in animals, for example, in humans. A compound that inhibits cAMPphosphodiesterase (PDE) can thereby increase intracellular levels ofcAMP, which in turn activate a protein kinase that phosphorylates atranscription factor (cAMP response binding protein). The phosphorylatedtranscription factor then binds to a DNA promoter sequence to activategenes that are important in long term memory. The more active such genesare, the better is long-term memory. Thus, by inhibiting aphosphodiesterase, long term memory can be enhanced.

Dementias are diseases that include memory loss and additionalintellectual impairment separate from memory. The compounds of thepresent invention are suitable for use in treating patients sufferingfrom memory impairment in all forms of dementia. Dementias areclassified according to their cause and include: neurodegenerativedementias (e.g., Alzheimer's, Parkinson's disease, Huntington's Disease,Pick's disease), vascular (e.g., infarcts, hemorrhage, cardiacdisorders), mixed vascular and Alzheimer's, bacterial meningitis,Creutzfeld-Jacob Disease, multiple sclerosis, traumatic (e.g., subduralhematoma or traumatic brain injury), infectious (e.g., HIV), genetic(down syndrome), toxic (e.g., heavy metals, alcohol, some medications),metabolic (e.g., vitamin B12 or folate deficiency), CNS hypoxia,Cushing's disease, psychiatric (e.g., depression and schizophrenia), andhydrocephalus.

The condition of memory impairment is manifested by impairment of theability to learn new information and/or the inability to recallpreviously learned information. The present invention includes methodsfor dealing with memory loss separate from dementia, including mildcognitive impairment (MCI) and age-related cognitive decline. Thepresent invention includes methods of treatment for memory impairment asa result of disease. Memory impairment is a primary symptom of dementiaand can also be a symptom associated with such diseases as Alzheimer'sdisease, schizophrenia, Parkinson's disease, Huntington's Disease,Pick's disease, Creutzfeld-Jakob disease, HIV, cardiovascular disease,and head trauma as well as age-related cognitive decline. The compoundsof the present invention are suitable for use in the treatment of memoryimpairment due to, for example, Alzheimer's disease, multiple sclerosis,amylolaterosclerosis (ALS), multiple systems atrophy (MSA),schizophrenia, Parkinson's disease, Huntington's Disease, Pick'sdisease, Creutzfeld-Jakob disease, depression, aging, head trauma,stroke, spinal cord injury, CNS hypoxia, cerebral senility, diabetesassociated cognitive impairment, memory deficits from early exposure ofanesthetic agents, multiinfarct dementia and other neurologicalconditions including acute neuronal diseases, as well as HIV andcardiovascular diseases.

The compounds of the present invention are also suitable for use in thetreatment of a class of disorders known as polyglutamine-repeatdiseases. These diseases share a common pathogenic mutation. Theexpansion of a CAG repeat, which encodes the amino acid glutamine,within the genome leads to production of a mutant protein having anexpanded polyglutamine region. For example, Huntington's Disease hasbeen linked to a mutation of the protein huntingtin. In individuals whodo not have Huntington's Disease, the protein huntingtin has apolyglutamine region containing about 8 to 31 glutamine residues. Forindividuals who have Huntington's Disease, the protein huntingtin has apolyglutamine region with over 37 glutamine residues. Aside fromHuntington's Disease (HD), other known polyglutamine-repeat diseases andthe associated proteins include dentatorubral-pallidoluysian atrophy,DRPLA (atrophin-1); spinocerebellar ataxia type-1 (ataxin-1);spinocerebellar ataxia type-2 (ataxin-2); spinocerebellar ataxia type-3(also called Machado-Joseph disease or MJD) (ataxin-3); spinocerebellarataxia type-6 (alpha 1a-voltage dependent calcium channel);spinocerebellar ataxia type-7 (ataxin-7); and spinal and bulbar muscularatrophy (SBMA, also know as Kennedy disease).

The basal ganglia are important for regulating the function of motorneurons; disorders of the basal ganglia result in movement disorders.Most prominent among the movement disorders related to basal gangliafunction is Parkinson's disease (Obeso et al., Neurology. 62(1 Suppl1):S17-30, 2004). Other movement disorders related to dysfunction of thebasal ganglia include tardive dyskinesia, progressive supranuclear palsyand cerebral palsy, corticobasal degeneration, multiple system atrophy,Wilson disease, dystonia, tics, and chorea. The compounds of theinvention are also suitable for use to treat movement disorders relatedto dysfunction of basal ganglia neurons.

PDE10 inhibitors are useful in raising cAMP or cGMP levels and preventneurons from undergoing apoptosis. PDE10 inhibitors may beanti-inflammatory by raising cAMP in glial cells. The combination ofanti-apoptotic and anti-inflammatory properties, as well as positiveeffects on synaptic plasticity and neurogenesis, make these compoundsuseful to treat neurodegeneration resulting from any disease or injury,including stroke, spinal cord injury, Alzheimer's disease, multiplesclerosis, amylolaterosclerosis (ALS), and multiple systems atrophy(MSA).

Autoimmune diseases or infectious diseases that affect the basal gangliamay result in disorders of the basal ganglia including ADHD, OCD, tics,Tourette's disease, Sydenham chorea. In addition, any insult to thebrain can potentially damage the basal ganglia including strokes,metabolic abnormalities, liver disease, multiple sclerosis, infections,tumors, drug overdoses or side effects, and head trauma. Accordingly,the compounds of the invention can be used to stop disease progressionor restore damaged circuits in the brain by a combination of effectsincluding increased synaptic plasticity, neurogenesis,anti-inflammatory, nerve cell regeneration and decreased apoptosis.

Testing

The PDE10 inhibitory activities of the compounds of the presentinvention can be tested, for example, using the in vitro and in vivo andex vivo assays described in the Biological Examples below.

Administration and Pharmaceutical Compositions

In general, the compounds of this invention can be administered in atherapeutically effective amount by any of the accepted modes ofadministration for agents that serve similar utilities. The actualamount of a compound of this invention, i.e., the active ingredient,depends upon numerous factors, such as the severity of the disease to betreated, the age and relative health of the subject, the potency of thecompound used, the route and form of administration, and other factors.

Therapeutically effective amounts of compounds of formula (I) may rangefrom approximately 0.1-1000 mg per day; preferably 0.5 to 250 mg/day,more preferably 3.5 mg to 70 mg per day.

In general, compounds of this invention can be administered aspharmaceutical compositions by any one of the following routes: oral,systemic (e.g., transdermal, intranasal or by suppository), orparenteral (e.g., intramuscular, intravenous or subcutaneous)administration. The preferred manner of administration is oral using aconvenient daily dosage regimen, which can be adjusted according to thedegree of affliction. Compositions can take the form of tablets, pills,capsules, semisolids, powders, sustained release formulations,solutions, suspensions, elixirs, aerosols, or any other appropriatecompositions.

The choice of formulation depends on various factors, such as the modeof drug administration (e.g., for oral administration, formulations inthe form of tablets, pills or capsules are preferred) and thebioavailability of the drug substance. Recently, pharmaceuticalformulations have been developed especially for drugs that show poorbioavailability based upon the principle that bioavailability can beincreased by increasing the surface area, i.e., decreasing particlesize. For example, U.S. Pat. No. 4,107,288 describes a pharmaceuticalformulation having particles in the size range from 10 to 1,000 nm inwhich the active material is supported on a crosslinked matrix ofmacromolecules. U.S. Pat. No. 5,145,684 describes the production of apharmaceutical formulation in which the drug substance is pulverized tonanoparticles (average particle size of 400 nm) in the presence of asurface modifier and then dispersed in a liquid medium to give apharmaceutical formulation that exhibits remarkably highbioavailability.

The compositions are comprised of, in general, a compounds of thepresent invention in combination with at least one pharmaceuticallyacceptable excipient. Acceptable excipients are non-toxic, aidadministration, and do not adversely affect the therapeutic benefit ofthe compounds of the present invention. Such excipient may be any solid,liquid, semi-solid or, in the case of an aerosol composition, gaseousexcipient that is generally available to one of skill in the art.

Solid pharmaceutical excipients include starch, cellulose, talc,glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silicagel, magnesium stearate, sodium stearate, glycerol monostearate, sodiumchloride, dried skim milk and the like. Liquid and semisolid excipientsmay be selected from glycerol, propylene glycol, water, ethanol andvarious oils, including those of petroleum, animal, vegetable orsynthetic origin, e.g., peanut oil, soybean oil, mineral oil, sesameoil, etc. Preferred liquid carriers, particularly for injectablesolutions, include water, saline, aqueous dextrose, and glycols.

Compressed gases may be used to disperse a compound of this invention inaerosol form. Inert gases suitable for this purpose are nitrogen, carbondioxide, etc.

Other suitable pharmaceutical excipients and their formulations aredescribed in Remington's Pharmaceutical Sciences, Gennaro, A. R. (MackPublishing Company, 18th ed., 1995).

The level of the compound in a formulation can vary within the fullrange employed by those skilled in the art. Typically, the formulationcontains, on a weight percent (wt %) basis, from about 0.01-99.99 wt %of a compounds of the present invention based on the total formulation,with the balance being one or more suitable pharmaceutical excipients.Preferably, the compound is present at a level of about 1-80 wt %.

The compounds can be administered as the sole active agent or incombination with other pharmaceutical agents such as other agents usedin the treatment of psychoses, especially schizophrenia and bipolardisorder, obsessive-compulsive disorder, Parkinson's disease,Alzheimer's disease, cognitive impairment and/or memory loss, e.g.,nicotinic α-7 agonists, PDE4 inhibitors, other PDE10 inhibitors, calciumchannel blockers, muscarinic m1 and m2 modulators, adenosine receptormodulators, ampakines, NMDA-R modulators, mGluR modulators, dopaminemodulators, serotonin modulators, canabinoid modulators, andcholinesterase inhibitors (e.g., donepezil, rivastigimine, andgalanthanamine). In such combinations, each active ingredient can beadministered either in accordance with their usual dosage range or adose below their usual dosage range, and can be administered eithersimultaneously or sequentially.

Drugs suitable in combination with the compounds of the presentinvention include, but are not limited to, other suitable schizophreniadrugs such as Clozaril, Zyprexa, Risperidone, and Seroquel; bipolardisorder drugs, including, but not limited to, Lithium, Zyprexa, andDepakote; Parkinson's disease drugs, including, but not limited to,Levodopa, Parlodel, Permax, Mirapex, Tasmar, Contan, Kemadin, Artane,and Cogentin; agents used in the treatment of Alzheimer's disease,including, but not limited to, Reminyl, Cognex, Aricept, Exelon,Akatinol, Neotropin, Eldepryl, Estrogen and Cliquinol; agents used inthe treatment of dementia, including, but not limited to, Thioridazine,Haloperidol, Risperidone, Cognex, Aricept, and Exelon; agents used inthe treatment of epilepsy, including, but not limited to, Dilantin,Luminol, Tegretol, Depakote, Depakene, Zarontin, Neurontin, Barbita,Solfeton, and Felbatol; agents used in the treatment of multiplesclerosis, including, but not limited to, Detrol, Ditropan XL,OxyContin, Betaseron, Avonex, Azothioprine, Methotrexate, and Copaxone;agents used in the treatment of Huntington's Disease, including, but notlimited to, Amitriptyline, Imipramine, Despiramine, Nortriptyline,Paroxetine, Fluoxetine, Setraline, Terabenazine, Haloperidol,Chloropromazine, Thioridazine, Sulpride, Quetiapine, Clozapine, andRisperidone; agents useful in the treatment of diabetes, including, butnot limited to, PPAR ligands (e.g. agonists, antagonists, such asRosiglitazone, Troglitazone and Pioglitazone), insulin secretagogues(e.g., sulfonylurea drugs, such as Glyburide, Glimepiride,Chlorpropamide, Tolbutamide, and Glipizide, and non-sulfonylsecretagogues), α-glucosidase inhibitors (such as Acarbose, Miglitol,and Voglibose), insulin sensitizers (such as the PPAR-γ agonists, e.g.,the glitazones; biguanides, PTP-1B inhibitors, DPP-IV inhibitors, and11beta-HSD inhibitors), hepatic glucose output lowering compounds (suchas glucagon antagonists and metaformin, e.g., Glucophage and GlucophageXR), insulin and insulin derivatives (both long and short acting formsand formulations of insulin); and anti-obesity drugs, including, but notlimited to, β-3 agonists, CB-1 agonists, neuropeptide Y5 inhibitors,Ciliary Neurotrophic Factor and derivatives (e.g., Axokine), appetitesuppressants (e.g., Sibutramine), and lipase inhibitors (e.g.,Orlistat).

Experimental

Unless otherwise noted, all materials were purchased from SinopharmChemical Reagent Co., Ltd and used without further purification. Allmicrowave assisted reactions were conducted with an Initiator®Synthesizer from Biotage®. All compounds showed NMR spectra consistentwith their assigned structures. Melting points were determined on aBuchi apparatus and are uncorrected. Mass spectral data was determinedby electrospray ionization technique. All examples were purified to >90%purity as determined by high-performance liquid chromatography. Unlessotherwise stated, reactions were run at room temperature.

General Schemes

The present invention further comprises procedures for the preparationof compounds of Formula (I). The compounds of Formula (I) can besynthesized according to the procedures described in the followingSchemes A or B, wherein p, q, R¹, R², R³, X¹ and X² are defined herein,except where further noted. The synthetic methods described below aremerely exemplary, and the compounds of the invention may also besynthesized by alternate routes as appreciated by persons of ordinaryskill in the art.

Preparation of Compound 2:

Preparation of Compound 1A:

Compound of formula 1a; wherein 1a G is an amino protecting group, suchas tert-Butyloxycarbonyl (Boc), can prepared according to processdescribed in WO 2011/143365; which can be followed by reacting with adeprotecting agent to afford compound of formula 1a; wherein G is Haccording to deprotection method known in the art.

A compound of formula (I) may be prepared by the method generallydescribed in General Scheme A. As shown, a compound of formula (I) maybe prepared by reacting a compound of formula 2, wherein LG₂ is aleaving group, such as triflate (CF₃SO₃ or OTf), halo (such as chloro),or nonafluorobutanesulfonate, with a compound of formula 4 in thepresence of a solvent, such as dimethyl sulfoxide (DMSO),N,N-dimethylformamide (DMF), or acetonitrile, in the presence of a base,such as diisopropylethyl amine (DIPEA), triethyl amine (TEA), orpotassium carbonate (K₂CO₃), at room temperature or up to 120° C.Compound of formula 4 can be prepared by reacting a compound of formula1a, wherein LG₁ is a leaving group, such as halo, preferably chloro, andG is hydrogen or an amino protecting group, such astert-Butyloxycarbonyl (Boc) or Carbobenzyloxy (Cbz), with a compound offormula 3 wherein M is boronic acid moiety or boronic ester moiety offormula —B(OH)₂ or —B(OR)₂ (wherein R is (C₁-C₄)alkyl)), Zn halide, orthe like, in the presence of a catalyst under a coupling reactioncondition, such as Suzuki reaction or Negeshi reaction. If G is an aminoprotecting group in the compound of formula 1a, the coupling reaction isfollowed by a deprotecting step by reacting a protected compound 4 withan amino deprotecting agent, such as concentrated, strong acid, such asHCl or CF₃COOH, or hydrogenolysis, to afford the compound of formula 4.

Preparation of Compound 2:

The compound of formula 2 that are not commercially available can bemade according to General Scheme A by reacting a compound of formula 6with an appropriate reagent and condition to afford a suitable leavinggroup LG₂. For example, a compound of formula 2a, wherein LG₂ istriflate (CF₃SO₃ or OTf) can be made by reacting a compound of formula 6with trifluoromethanesulfonic anhydride (Tf₂O). Alternatively, acompound of formula 2b, wherein LG₂ is halo (such as chloro) can be madeby reacting a compound of formula 6 with Phosphorus(V) oxychloride(POCl₃). Alternatively, a compound of formula 2c, wherein LG₂ isnonafluorobutanesulfonate, can be made by reacting a compound of formula6 with 1-butanesulfonylfluoride C₄F₉SO₂F). Compound 6 is commerciallyavailable or can be readily prepared according to the methods describedherein.

Preparation of Compound 3:

The compound of formula 3 wherein M is —B(OH)₂ is commerciallyavailable. It can also be made according to General Scheme A by reactingthe corresponding commercially available chloro- or bromo precursorcompound with an appropriate catalyst and metalation agent and underappropriate condition to afford a suitable metal (M) moiety. Forexample, a compound of formula 3, wherein M is —B(OH)₂, can be made byreacting the corresponding bromo-precursor compound with PdCl₂(PPh)₃catalyst in the presence of Bis(pinacolato)diboron (C₁₂H₂₄B₂O₄) andpotassium acetate in non polar solvent, such as dioxane, at elevatedtemperature followed by conversion of the resulting pinacol boronate tothe corresponding boronic acid.

Alternatively a compound of formula (I) may be made by the methodgenerally described in General Scheme B. As shown, a compound of formula(I) may be made by reacting a compound of formula 5, wherein LG₁ is aleaving group, such as triflate (CF₃SO₃ or OTf) or halo (such as chloro)with a compound of formula 3, wherein M is boronic acid moiety orboronic ester moiety of formula —B(OH)₂ or —B(OR)₂ (wherein R is(C₁-C₄)alkyl)), Zn halide, or the like, in the presence of a catalystunder a coupling reaction condition, such as Suzuki reaction or Negeshireaction. Compound of formula 5 can be made by reacting a compound offormula 1b, wherein LG₁ is a leaving group, such as triflate (CF₃SO₃ orOTf) or halo (such as chloro), with a compound of formula 2 wherein LG₂is a leaving group, such as triflate (CF₃SO₃ or OTf), halo (such aschloro), or nonafluorobutanesulfonate, in the presence of a solvent,such as DMSO, DMF, or acetonitrile, in the presence of a base, such asDIPEA, TEA, or K₂CO₃, at room temperature or up to 120° C.

Compounds of Formulas 1b, 2, 3 can be prepared according to GeneralScheme A.

SYNTHETIC EXAMPLES

The following list of abbreviations used or commonly used throughout thespecification represent the following and should assist in understandingthe invention:

-   ACN, MeCN acetonitrile-   Aq., aq. aqueous-   Ar argon (gas)-   BOP benzotriazol-1-yl-oxy Hexafluorophosphate-   BuLi Butyllithium-   Cs₂CO₃ cesium carbonate-   CHCl₃ chloroform-   CH₂Cl₂, DCM dichloromethane, methylene chloride-   Cu(1)I copper(1) iodide-   DCC dicyclohexylcarbodiimide-   DIC 1,3-diisopropylcarbodiimide-   DIEA, DIPEA diisopropylethylamine-   DME dimethoxyethane-   DMF dimethylformamide-   DMAP 4-dimethylaminopyridine-   DMS dimethylsulfide-   DMSO dimethylsulfoxide-   EDC, EDCI 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide-   Et₂O diethyl ether-   EtOAc ethyl acetate-   FBS fetal bovine serum-   G, gm gram-   h, hr hour-   H₂ hydrogen-   H₂O water-   HCl hydrochloric acid-   HOAc acetic acid-   HPLC high pressure liquid chromatography-   IPA, IpOH isopropyl alcohol-   K₂CO₃ potassium carbonate-   KI potassium iodide-   LG leaving group-   LDA Lithium diisopropylamide-   LiOH lithium hydroxide-   MgSO₄ magnesium sulfate-   MS or m/z mass spectrum-   MeOH methanol-   N₂ nitrogen-   NaCNBH₃ sodium cyanoborohydride-   Na₂CO₃ sodium carbonate-   NaHCO₃ sodium bicarbonate-   NaH sodium hydride-   Nat sodium iodide-   NaBH₄ sodium borohydride-   NaOH sodium hydroxide-   Na₂SO₄ sodium sulfate-   NH₄Cl ammonium chloride-   NH₄OH ammonium hydroxide-   P(t-bu)₃ tri(tert-butyl)phosphine-   PBS phosphate buffered saline-   Pd/C palladium on carbon-   Pd(PPh₃)₄ palladium(0)triphenylphosphine tetrakis-   Pd(dppf)Cl₂ palladium(1,1-bisdiphenylphosphinoferrocene)(II)chloride-   Pd(PhCN)₂Cl₂ palladium di-cyanophenyl dichloride-   Pd(OAc)₂ palladium acetate-   Pd₂(dba)₃ tris(dibenzylideneacetone) dipalladium-   RT, rt room temperature-   RBF, rbf round bottom flask-   TLC, tlc thin layer chromatography-   TEA, Et₃N triethylamine-   TFA trifluoroacetic acid-   THF tetrahydrofuran

The following preparations of compounds of Formula (I) and intermediates(References) are given to enable those skilled in the art to moreclearly understand and to practice the present invention. They shouldnot be considered as limiting the scope of the invention, but merely asbeing illustrative and representative thereof.

Example 14-(3-(1-(7-chloroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

Step 1: tert-butyl4-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)piperidine-1-carboxylate

To a round bottomed flask (RBF) was added tert-butyl4-(3-chloropyrazin-2-yl)piperidine-1-carboxylate (2 g, 6.72 mmol),(3-fluoro-4-(methylcarbamoyl)phenyl)boronic acid (1.64 g, 8.33 mmol;Combi-Blocks), potassium phosphate (3.56 g, 16.79 mmol),Bis(di-tert-butyl(4-dimethylaminophenyl)phosphine)dichloropalladium(II)(0.476 g, 0.672 mmol), and dioxane (20 mL):Water (2 mL). The mixture wasstirred at 90° C. After 16 h, the reaction was allowed to cool to roomtemperature and poured into water (50 mL). The aqueous solution wasextracted with ethyl acetate (EtOAc) (3×25 mL). The combined EtOAclayers were concentrated in vacuo and adsorbed onto a plug of silica geland chromatographed through a Redi-Sep® pre-packed silica gel column (40g), eluting with 30-100% EtOAc in hexane, to provide tert-butyl4-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)piperidine-1-carboxylate(2.46 g, 5.94 mmol, 88% yield), as a yellow solid.

Step 2: 2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamidetrihydrochloride

To a RBF was added tert-butyl4-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)piperidine-1-carboxylate(2.40 g, 5.79 mmol) and methanol (20 mL) was added 4M HCl in dioxane (5mL, 20.00 mmol). The solution was stirred at room temperature. After 96h, the reaction was concentrated in vacuo to give2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamidetrihydrochloride (2.46 g, 5.81 mmol, 100% yield), as a yellow foam. The3 HCl equivalent was determined from the weight of the compound, withoutfurther characterization.

Step 3:4-(3-(1-(7-chloroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

To a mixture of2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamidetrihydrochloride (315 mg, 0.743 mmol), 2,7-dichloroquinoline (192 mg,0.969 mmol), cesium carbonate (1211 mg, 3.72 mmol), dioxane (4 mL), andbis(tri-t-butylphosphine)palladium(0) (89 mg, 0.174 mmol). The solutionwas stirred at 90° C. After stirring for 5 h, the reaction was allowedto cool to room temperature and filtered. The solids were washed withEtOAc. The filtrate was concentrated to ½ it's original volume andpurified by reverse-phase preparative HPLC (Shimadzu) on a PhenomenexGemini column (10 micron, C18, 110 Å, Axia, 100×50 mm) eluting at 90mL/min with a linear gradient of 10-60% MeCN (0.1% TFA) in water (0.1%TFA) over 20 min. The desired fractions were poured into 10% Na₂CO₃ andextracted with dichloromethane (DCM) (8×10 mL). The combined DCM layerswere dried over MgSO₄ and concentrated in vacuo to give4-(3-(1-(7-chloroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide(135 mg, 0.284 mmol, 38.2% yield), as an off white solid. m/z=476 (M+1).¹H NMR (300 MHz, CDCl₃) δ 8.54 (d, J=2.34 Hz, 1H), 8.49 (d, J=2.34 Hz,1H), 8.27 (t, J=8.04 Hz, 1H), 7.83 (d, J=9.35 Hz, 1H), 7.67 (d, J=2.05Hz, 1H), 7.49 (d, J=8.62 Hz, 1H), 7.44 (dd, J=1.46, 8.04 Hz, 1H), 7.35(dd, J=1.46, 12.42 Hz, 1H), 7.15 (dd, J=2.05, 8.48 Hz, 1H), 6.98 (d,J=9.35 Hz, 1H), 6.79 (d, J=6.28 Hz, 1H), 4.68 (d, J=13.30 Hz, 2H),3.16-3.31 (m, 1H), 3.09 (dd, J=0.80, 4.75 Hz, 3H), 2.86-3.02 (m, 2H),2.01-2.19 (m, 2H), 1.82 (d, J=11.55 Hz, 2H).

Example 22-fluoro-4-(3-(1-(7-fluoroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-N-methylbenzamide

Step 1. (E)-methyl 3-(2-amino-4-fluorophenyl)acrylate

To a mixture of 2-bromo-5-fluoroaniline (35.00 g, 184 mmol, Aldrich),palladium (II) acetate (2.06 g, 9.18 mmol, Strem) andtri(o-tolyl)phosphine (5.60 g, 18.40 mmol; Strem) in acetonitrile (350ml) at RT was added methyl acrylate (33.00 ml, 365 mmol, Aldrich) andtriethylamine (64.00 ml, 460 mmol, Aldrich). The reaction was heated at80° C. for 24 h. The reaction mixture was diluted with EtOAc (500 mL)and the resulting colorless crystalline solid was filtered and washedwith EtOAc. The organic solution was concentrated to dryness and thesolids were slurried in 10% EtOAc/hexane at 60° C. for 1 h. The slurrywas cooled to RT and filtered. The solid was washed with 10%EtOAc/hexane and sucked dry with air to give 18.30 g (51%) of alight-yellow crystalline solid. m/z=195.9 (M+1).

Step 2. 7-fluoroquinolin-2(1H)-one

A mixture of (E)-methyl 3-(2-amino-4-fluorophenyl)acrylate (30.38 g, 156mmol) in THF (400 mL) and 3M hydrochloric acid (400 mL) was heated at65° C. for 20 h. The mixture was cooled to RT and poured onto ice. Theresulting precipitate was filtered, washed with copious amounts of waterand dried in vacuo to give 20.65 g (81%) of a light-yellow amorphoussolid. m/z=164 (M+1).

Step 3. 7-fluoroquinolin-2-yl trifluoromethanesulfonate

To a cooled (0° C.) solution of 7-fluoroquinolin-2(1H)-one (1.60 g, 9.81mmol) in pyridine (40 mL) was added trifluoromethanesulfonic anhydride(2.2 mL, 13.10 mmol, Aldrich) via syringe. After complete addition, thereaction was allowed to warm to RT and stirred for 1 h. The solvent wasremoved in vacuo and the residue was azeotroped with toluene. Theresidue was stirred vigorously over Et₂O, filtered and washed with Et₂O.The filtrate was concentrated to dryness to give 2.50 g (86%) of anorange oil. m/z=295.9 (M+1).

Step 4.2-fluoro-4-(3-(1-(7-fluoroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-N-methylbenzamide

To a RT solution of2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamidetrihydrochloride (1.00 g, 3.18 mmol, prepared according to Step 2 ofExample 1) and triethylamine (2.00 ml, 14.35 mmol) in DMSO (10 ml) wasadded a solution of 7-fluoroquinolin-2-yl trifluoromethanesulfonate(1.10 g, 3.73 mmol, prepared according to Step 3 of Example 2) in DMSO(2 mL). The reaction mixture was heated at 60° C. for 2.5 h. Thereaction was cooled RT and diluted with water. The mixture was extractedwith CH₂Cl₂ (3×). The combined organic layers were washed with brine anddried over Na₂SO₄. The solution was filtered and the solution wasevaporated onto silica gel and purified by flash chromatography (Isco(80 gram)) eluting with EtOAc:hexanes (0:1→3:1). The fractionscontaining product were concentrated in vacuo and the residue wasstirred vigorously over Et₂O for 3 h. The solid was filtered, washedwith Et₂O and dried to give 674 mg (46%) of the desired product. m/z=460(M+1). ¹H NMR (300 MHz, DMSO-d₆) δ ppm 8.62 (d, J=2.34 Hz, 1 H), 8.59(d, J=2.34 Hz, 1 H), 8.39 (br. s., 1 H), 8.04 (d, J=9.21 Hz, 1 H),7.69-7.83 (m, 2 H), 7.45-7.58 (m, 2 H), 7.18-7.28 (m, 2 H), 7.08 (td,J=8.77, 2.63 Hz, 1 H), 4.66 (d, J=13.30 Hz, 2 H), 3.13-3.29 (m, 1 H),2.86-3.03 (m, 2 H), 2.82 (d, J=4.68 Hz, 3 H), 1.72-1.97 (m, 4 H).

Example 32-fluoro-N-methyl-4-(3-(1-(quinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)benzamide

The title compound was prepared in an analogous manner to Example 1 byusing 7-chloroquinoline in place of 2,7-dichloroquinoline in Step 3 togive2-fluoro-N-methyl-4-(3-(1-(quinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)benzamide(49 mg, 0.111 mmol, 23.5% yield), as a light yellow solid. m/z=442(M+1). ¹H NMR (300 MHz, CDCl₃) δ ppm 8.54 (d, J=2.34 Hz, 1H), 8.49 (d,J=2.34 Hz, 1H), 8.26 (t, J=8.04 Hz, 1H), 7.88 (d, J=9.21 Hz, 1H), 7.69(d, J=8.33 Hz, 1H), 7.59 (d, J=8.04 Hz, 1H), 7.52 (dt, J=1.46, 7.67 Hz,1H), 7.44 (dd, J=1.53, 7.97 Hz, 1H), 7.36 (dd, J=1.53, 12.35 Hz, 1H),7.15-7.25 (m, 1H), 7.01 (d, J=9.21 Hz, 1H), 6.78 (br. s., 1H), 4.68 (d,J=13.15 Hz, 2H), 3.14-3.29 (m, 1H), 3.03-3.14 (m, 3H), 2.82-3.03 (m,2H), 2.03-2.23 (m, 2H), 1.83 (d, J=11.84 Hz, 2H).

Example 42-fluoro-4-(3-(1-(6-fluoroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-N-methylbenzamide

To a solution of2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamide (155 mg,0.493 mmol, prepared according to Step 2 of Example 1),2-chloro-6-fluoroquinoline (108 mg, 0.595 mmol, Combi-blocks), and DMSO(2 mL) was added potassium carbonate (240 mg, 1.737 mmol). The solutionwas stirred at 100° C. After 72 h, the reaction was allowed to cool toroom temperature and diluted with water (50 mL). After stirring for 30min, the solution was filtered and the filtered solid adsorbed onto aplug of silica gel and chromatographed through a Redi-Sep® pre-packedsilica gel column (12 g), eluting with 0-80% EtOAc in hexane, to providea light yellow solid, which contained residual DMSO as measure by NMR.The solids were redissolved in diethyl ether and washed with water,brine, and concentrated in vacuo to give2-fluoro-4-(3-(1-(6-fluoroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-N-methylbenzamide(90 mg, 0.196 mmol, 39.7% yield), as a light yellow solid. m/z=460(M+1). ¹H NMR (300 MHz, CDCl₃) δ ppm 8.55 (d, J=2.48 Hz, 1H), 8.49 (d,J=2.48 Hz, 1H), 8.26 (t, J=8.04 Hz, 1H), 7.82 (d, J=9.21 Hz, 1H), 7.65(dd, J=5.26, 9.06 Hz, 1H), 7.44 (dd, J=1.61, 8.04 Hz, 1H), 7.36 (dd,J=1.61, 12.42 Hz, 1H), 7.28-7.32 (m, 1H), 7.22 (dd, J=2.92, 8.92 Hz,1H), 7.04 (d, J=9.21 Hz, 1H), 6.77 (br. s., 1H), 4.64 (d, J=13.45 Hz,2H), 3.14-3.31 (m, 1H), 3.03-3.14 (m, 3H), 2.81-3.02 (m, 2H), 2.05-2.21(m, 2H), 1.82 (d, J=11.69 Hz, 2H).

Example 52-fluoro-4-(3-(1-(8-fluoroquinolin-2-yl)piperidin-4-yl)pyrazin-2-yl)-N-methylbenzamide

The title compound was prepared analogously to Example 8 by using2-chloro-8-fluoroquinoline (Combi-blocks) and2-fluoro-N-methyl-4-(3-(piperidin-4-yl)pyrazin-2-yl)benzamidetrihydrochloride (prepared according to Step 2 of Example 1) in Step 3.¹H NMR (400 MHz, chloroFORM-d) δ ppm 1.85 (d, J=11.93 Hz, 2 H) 2.04-2.19(m, 2 H) 2.91-3.03 (m, 2 H) 3.09 (d, J=4.50 Hz, 3 H) 3.22 (tt, J=11.61,3.74 Hz, 1 H) 4.72 (d, J=13.50 Hz, 2 H) 6.80 (d, J=7.43 Hz, 1 H) 7.05(d, J=9.19 Hz, 1 H) 7.08-7.15 (m, 1 H) 7.20-7.25 (m, 1 H) 7.32-7.39 (m,2 H) 7.44 (dd, J=8.02, 1.37 Hz, 1 H) 7.88 (dd, J=9.19, 1.17 Hz, 1 H)8.27 (t, J=8.02 Hz, 1 H) 8.50 (d, J=2.35 Hz, 1 H) 8.55 (d, J=2.35 Hz, 1H). m/z=460 (M+1).

Example 62-fluoro-N-methyl-4-(3-(1-(quinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)benzamide

Step 1. 2-(3-(3-chloropyrazin-2-yl)azetidin-1-yl)quinazoline

2-(Azetidin-3-yl)-3-chloropyrazine hydrochloride (1.50 g, 7.28 mmol),2-chloroquinazoline (1.20 g, 7.28 mmol, Parkway Scientific), and cesiumcarbonate (5.22 g, 16.0 mmol, Fluka) were mixed in DMF (30 mL) in around bottom flask under a nitrogen atmosphere. The mixture was stirredat 110° C. for 17 h. The reaction mixture was cooled to roomtemperature, diluted with water, and extracted with EtOAc (2×). Thecombined organic extracts were washed with saturated sodium chloride,dried over magnesium sulfate, filtered, and concentrated in vacuo. Theresulting crude mixture was purified via silica gel flash columnchromatography eluting with 0% to 100% EtOAc in hexanes to give 1.02 g(47%) of a yellow amorphous solid. ¹H NMR (400 MHz, chloroFORM-d) δ ppm4.41-4.50 (m, 1 H) 4.58-4.63 (m, 2 H) 4.65-4.72 (m, 2 H) 7.22-7.28 (m, 1H) 7.61-7.72 (m, 3 H) 8.28 (d, J=2.35 Hz, 1 H) 8.51 (d, J=2.35 Hz, 1 H)9.04 (s, 1 H). m/z=298 (M+1).

Step 2.2-fluoro-N-methyl-4-(3-(1-(quinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)benzamide

(0.400 g, 1.34 mmol), (3-fluoro-4-(methylcarbamoyl)phenyl)boronic acid(0.318 g, 1.61 mmol, Combi-Blocks), andtrans-dichlorobis(triphenylphosphine)palladium (ii) (0.019 g, 0.027mmol, Strem) were mixed in 1,4-Dioxane (6 mL) in a round bottom flaskunder an argon atmosphere. Sodium carbonate (2.02 mL, 4.03 mmol, 2.0 Maqueous solution) was added, and the reaction mixture was stirred at 80°C. for 3.5 h. The reaction mixture was cooled to room temperature,diluted with water, and extracted with EtOAc. The organic layer wasseparated, washed with saturated sodium chloride, dried over magnesiumsulfate, filtered, and concentrated in vacuo. The resulting crudemixture was purified via silica gel flash column chromatography elutingwith 50% to 100% EtOAc in hexanes to give 557 mg (86%) of the titlecompound as a light yellow solid. ¹H NMR (400 MHz, chloroFORM-d) δ ppm3.09 (d, J=4.69 Hz, 3 H) 4.29-4.39 (m, 1 H) 4.48-4.58 (m, 4 H) 6.75-6.86(br. m., 1 H) 7.22-7.28 (m, 1 H) 7.36 (d, J=12.52 Hz, 1 H) 7.41 (dd,J=8.02, 1.17 Hz, 1 H) 7.60-7.72 (m, 3 H) 8.27 (t, J=8.02 Hz, 1 H) 8.57(d, J=2.15 Hz, 1 H) 8.65 (d, J=2.15 Hz, 1 H) 9.02 (s, 1 H).m/z=415(M+1).

Example 72-fluoro-N-methyl-4-(3-(1-(quinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)benzamide

A mixture of 2-(3-(3-chloropyrazin-2-yl)azetidin-1-yl)quinoline (0.072g, 0.243 mmol; see preparation in WO2011143365),(3-fluoro-4-(methylcarbamoyl)phenyl)boronic acid (0.076 g, 0.388 mmol,Combi-blocks), potassium phosphate (0.129 g, 0.607 mmol, Alfa Aesar),bis(di-tert-butyl(4-dimethylaminophenyl)phosphine)dichloropalladium (II)(0.017 g, 0.024 mmol, Aldrich), water (0.3 mL) and dioxane (1.2 mL) waspurged with Argon gas. The mixture was heated at 100° C. for 30 min inmicrowave reactor, then the heating was stopped and the mixture wascooled to room temperature. The mixture was diluted with saturatedNa₂CO₃ and extracted with EtOAc three times. The organic layer was driedover Na₂SO₄ and concentrated in vacuo. The crude was purified by silicagel chromatography (12 g, 0%-100% EtOAc-CH₂Cl₂). The product was furtherpurified by reverse phase HPLC (Shimazu; Gemini 10 μM C18 110A AXIA,100×50 mm column, 10-55% MeCN in water with 0.1% TFA in 26 min). Thecollected fractions were neutralized with solid Na₂CO₃ and extractedwith CH₂Cl₂ three times. The organic phase was dried over Na₂SO₄ andconcentrated in vacuo. The product was obtained as a white solid (73 mg,73%). ¹H NMR (400 MHz, chloroFORM-d) δ ppm 3.10 (d, J=4.69 Hz, 3 H)4.30-4.55 (m, 5 H) 6.63 (d, J=8.80 Hz, 1 H) 6.83 (d, J=7.04 Hz, 1 H)7.23 (t, J=7.34 Hz, 1 H) 7.37 (d, J=12.32 Hz, 1 H) 7.42 (dd, J=8.02,1.17 Hz, 1 H) 7.50-7.57 (m, 1 H) 7.61 (d, J=7.82 Hz, 1 H) 7.73 (d,J=8.41 Hz, 1 H) 7.89 (d, J=8.80 Hz, 1 H) 8.28 (t, J=8.02 Hz, 1 H) 8.57(d, J=2.35 Hz, 1 H) 8.64 (d, J=2.35 Hz, 1 H). m/z=414 (M+1).

Example 82-fluoro-4-(3-(1-(7-fluoroquinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-N-methylbenzamide

Step 1: tert-butyl3-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)azetidinE-1-carboxylate

The compound was prepared analogously to Example 1 by using(3-fluoro-4-(methylcarbamoyl)phenyl)boronic acid (purchased from CombiBlocks) and tert-butyl 3-(3-chloropyrazin-2-yl)azetidine-1-carboxylate.m/z=287 (M+1-100).

Step 2: 4-(3-(azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetris(2,2,2-trifluoroacetate)

To a mixture of tert-butyl3-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)azetidine-1-carboxylate(5.19 g, 13.43 mmol), prepared according to Step 1 of Example 8, andCH₂Cl₂ (20 mL) was added trifluoroacetic acid (7.24 mL, 94.00 mmol). Themixture was stirred at room temperature for 1 h. LCMS showed theproduct. The mixture was concentrated in vacuo. CH₂Cl₂ was added andevaporated to remove extra TFA. Ether was added and evaporated. Theproduct was obtained as a yellow oil after drying on vacuum overnightand used in next step without purification. m/z=287 (M+1).

Step 3:2-fluoro-4-(3-(1-(7-fluoroquinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-N-methylbenzamide

A mixture of4-(3-(azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetris(2,2,2-trifluoroacetate) (0.953 g, 1.517 mmol), potassium carbonate(0.839 g, 6.070 mmol), 7-fluoroquinolin-2-yl trifluoromethanesulfonate(0.537 g, 1.821 mmol, prepared according to Step 3 of Example 2), andDMSO (10 mL) was stirred at 50° C. for 1 h. LCMS showed the product andno more azetidine starting material. The mixture was diluted with waterand extracted with CH₂Cl₂ three times. The organic layer was dried overNa₂SO₄ and concentrated in vacuo. The crude was purified by silica gelchromatography: 40 g, 5-100% EtOAc-hexane. The impurity2-hydroxyquinoline was further removed by trituration with CH₂Cl₂ andhexane twice. The product was obtained as a white solid (510 mg, 78%).¹H NMR (400 MHz, chloroFORM-d) δ ppm 3.09 (d, J=4.50 Hz, 3 H) 4.33-4.50(m, 5 H) 6.56 (d, J=9.00 Hz, 1 H) 6.81 (d, J=7.04 Hz, 1 H) 6.98 (td,J=8.61, 2.54 Hz, 1 H) 7.31-7.45 (m, 3 H) 7.56 (dd, J=8.71, 6.36 Hz, 1 H)7.84 (d, J=9.00 Hz, 1 H) 8.28 (t, J=8.02 Hz, 1 H) 8.57 (d, J=2.15 Hz, 1H) 8.64 (d, J=2.35 Hz, 1 H). m/z=432 (M+1 ).

Example 92-fluoro-4-(3-(1-(7-fluoroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-N-methylbenzamide

The title compound was prepared analogously to Example 8 by using2-chloro-7-fluoroquinazoline (Activate Scientific) in Step 3. ¹H NMR(400 MHz, chloroFORM-d) δ ppm 3.01-3.15 (m, 3 H) 4.25-4.40 (m, 1 H)4.43-4.61 (m, 4 H) 6.99 (td, J=8.71, 2.15 Hz, 1 H) 7.23 (dd, J=10.66,1.86 Hz, 1 H) 7.31-7.45 (m, 2 H) 7.67 (dd, J=8.61, 6.26 Hz, 1 H) 8.27(t, J=8.02 Hz, 1 H) 8.57 (d, J=2.15 Hz, 1 H) 8.66 (d, J=2.15 Hz, 1 H)8.96 (s, 1 H). m/z=433 (M+1).

Example 104-(3-(1-(7-chloroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

Steps 1-4: 2,7-dichloroquinazoline Step 1:(2-amino-4-chlorophenyl)methanol

In a 500 mL round bottom flask, the stirred solution of2-amino-4-chlorobenzoic acid (42.8 g, 250.29 mmol, Aldrich) wasdissolved anhydrous THF (200 mL) and the solution was cooled in anice-bath. Lithium aluminum hydride (11.76 g, 312.86 mmol) was addedportionwise to the above solution at the ice-bath temperature undernitrogen atmosphere. The resulting mixture was stirred at rt for 8 h. Oncompletion of reaction the reaction mixture was cooled to ice-bathtemperature and quenched by sequential addition of cold water (12 mL),15% NaOH (12 mL) and water (36 mL). The resulting slurry was stirred atrt for 30 min and filtered through a CELITE™ pad. The solid residue waswashed with ethyl acetate (1000 mL) and combined filtrate wasconcentrated under reduced pressure to give (2-amino4-chlorophenyl)methanol as an off white solid. Yield: 32 g (81.6%). LCMS(ESI, m/z): 181 (M+23)⁺

Step 2. 2-amino-4-chlorobenzaldehyde

In a 2 L 3-neck round bottom flask, the stirred solution of(2-amino-4-chlorophenyl)methanol 2 (32 g, 203.82 mmol) in DCM (765 mL),manganese (IV) oxide (150 g, 1.724 mol) was added at rt. The resultingreaction mixture was stirred at rt under argon atmosphere for 40 h. Oncompletion of reaction the reaction mixture was filtered through CELITE™pad and solid residue was washed thoroughly with DCM (1000 mL). Thecombined filtrate was concentrated under reduced pressure to give2-amino-4-chlorobenzaldehyde as orange solid.

Yield: 24 g (76.2%).

Step 3: 7-chloroquinazolin-2-ol

In a 500 mL round bottom flask, the uniform mixture of2-amino-4-chlorobenzaldehyde (16 g, 103.2 2 mmol) and urea (123.8 g,2063 mmol) was heated at 170° C. with vigorous stirring for 2 h. Oncompletion of reaction, the reaction mixture was cooled to rt anddiluted with ice-cold water. The solid that formed was collected byfiltration and washed with ice-cold water. The solid was dried underreduced pressure to give crude 7-chloroquinazolin-2-ol as a yellowsolid. Yield: 19 g. LCMS (ESI, m/z): 181 (M+1)+

Step 4: 2,7-dichloroquinazoline

In a 250 mL three neck round bottom flask, 7-chloroquinazolin-2-ol (19g, 105.55 mmol) was suspended in freshly distilled POCl₃ (190 mL) at rt.The resulting suspension was heated to 110° C. for 4 h. On completion ofreaction, the reaction mixture was cooled to rt and concentrated underreduced pressure. The residue obtained was diluted with ethyl acetate(200 mL) and cold water (200 mL). The organic layer was separated andthe aqueous phase was re-extracted with ethyl acetate (500 mL×2). Thecombined EtOAc extract was washed with brine and concentrated underreduced pressure. The residue (pale brown) obtained was purified bysilica gel (60-120 mesh) column chromatography and gradient elution with12-20% ethyl acetate-hexanes gave 2,7-dichloroquinazoline as a paleyellow solid. Yield: 7 g (33.5%). LCMS (ESI, m/z): 199 (M+1)+.

Step 5: 4-(3-(azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetris(2,2,2-trifluoroacetate)

To a mixture of tert-butyl3-(3-(3-fluoro-4-(methylcarbamoyl)phenyl)pyrazin-2-yl)azetidine-1-carboxylate(5.19 g, 13.43 mmol) and DCM (20 mL) was added 2,2,2-trifluoroaceticacid (7.24 mL, 94 mmol). The mixture was stirred at rt for 1 h. Themixture was concentrated in vacuo. DCM was added and evaporated toremove extra TFA. Ether was added and evaporated. The product wasobtained as a yellow oil after drying on vacuum overnight. MS: 287(M+1).

Step 6:4-(3-(1-(7-chloroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

4-(3-(Azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetris(2,2,2-trifluoroacetate) (0.150 g, 0.239 mmol),2,7-dichloroquinazoline (0.062 g, 0.310 mmol), and potassium carbonate(0.165 g, 1.19 mmol, Aldrich) were mixed in butan-1-ol (2 mL) in asealed tube. The reaction mixture was stirred at 110° C. for 18 h. Thereaction mixture was cooled to room temperature, diluted with water, andextracted with EtOAc. The organic layer was separated, washed withsaturated sodium chloride, dried over magnesium sulfate, filtered, andconcentrated in vacuo. The resulting crude mixture was purified viasilica gel flash column chromatography eluting with 50% to 100% EtOAc inhexanes to yield give 99 mg (92%) of a light yellow solid. ¹H NMR (400MHz, chloroFORM-d) δ ppm 3.09 (d, J=4.50 Hz, 3 H) 4.29-4.38 (m, 1 H)4.46-4.58 (m, 4 H) 6.75-6.85 (br. m., 1 H) 7.18 (dd, J=8.61, 1.56 Hz, 1H) 7.36 (d, J=12.32 Hz, 1 H) 7.40 (dd, J=8.12, 1.27 Hz, 1 H) 7.60 (d,J=8.41 Hz, 1 H) 7.63 (br. s., 1 H) 8.27 (t, J=8.02 Hz, 1 H) 8.57 (d,J=2.15 Hz, 1 H) 8.65 (d, J=2.15 Hz, 1 H) 8.97 (s, 1 H). m/z=449 (M+1).

Example 112-fluoro-4-(3-(1-(6-fluoroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-N-methylbenzamide

The title compound was prepared analogously to Example 8 by using6-fluoroquinazolin-2-yl trifluoromethanesulfonate in place of7-fluoroquinolin-2-yl trifluoromethanesulfonate in Step 3 and purifiedby reverse phase HPLC. The pure fractions were concentrated to minimalH₂O, neutralized by saturated aqueous NaHCO₃. The solid was collected byfiltration, washed with H₂O to give the title compound (49 mg, 51%). ¹HNMR (400 MHz, DMSO-d₆) δ ppm 9.19 (1 H, s), 8.73 (1 H, d, J=2.3 Hz),8.67 (1 H, d, J=2.3 Hz), 8.32-8.45 (1 H, m), 7.78 (1 H, t, J=7.6 Hz),7.62-7.71 (2 H, m), 7.51-7.62 (2 H, m), 7.49 (1 H, dd, J=7.9, 1.5 Hz),4.23-4.47 (5 H, m), 2.82 (3 H, d, J=4.5 Hz). m/z=433 (M+1).

Example 124-(3-(1-(7-chloro-6-fluoroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

Step 1 & 2: 4-chloro-5-fluoro-2-nitrobenzaldehyde

STEP 1. Borane methyl sulfide, complex (2.81 mL, 29.7 mmol) was addedvia syringe to a solution of trimethyl borate (26.5 mL, 237 mmol) and4-chloro-5-fluoro-2-nitrobenzoic acid (6.51 g, 29.7 mmol) in THF (75 mL)under argon. The mixture was stirred at reflux for 6 h, then cooled to0° C. MeOH (50 mL) was added dropwise and the mixture was stirred for 30min at RT. The solvent was then removed in vacuo and the resulting oilwas purified by silica gel to give alcohol as a solid, which was takendirectly to the next step.

STEP 2. The material produced above was dissolved in DCM 100 mL andmanganese (iv) oxide (2.58 g, 29.7 mmol) was added. The mixture wasstirred overnight at RT, and then the manganese (iv) oxide was removedby filtration though CELITE™. The Titrate was then concentrated in vacuoand purified by silica gel chromatography to give4-chloro-5-fluoro-2-nitrobenzaldehyde as a yellow solid. (1.32 g, 78%yield for 2 steps). ¹H NMR (400 MHz, DMSO-d6) δ ppm 7.94 (d, J=8.80 Hz,1 H) 8.55 (d, J=6.26 Hz, 1 H) 10.18 (d, J=1.96 Hz, 1 H).

Step 3. 2-amino-4-chloro-5-fluorobenzaldehyde

A mixture of 4-chloro-5-fluoro-2-nitrobenzaldehyde (1.50 g, 7.37 mmol),concentrated hydrochloric acid (0.30 ml, 3.68 mmol), and iron (1.32 g,23.6 mmol) in EtOH (18 mL), AcOH (18 mL), and water (9 mL) was heated toreflux for 30 minutes, then cooled to RT. The resulting suspension wasfiltered through CELITE™ and the filtrate was then partitioned betweenEtOAc and water. The layers were separated, the organic layer was washedwith saturated aqueous sodium bicarbonate solution, dried over anhydrousmagnesium sulfate, filtered, and concentrated in vacuo to give2-amino-4-chloro-5-fluorobenzaldehyde as a yellow solid (1.15 g, 90%yield). m/z=174 (M+1).

Step 4. 2,7-dichloro-6-fluoroquinazoline

A mixture of 2-amino-4-chloro-5-fluorobenzaldehyde (0.30 g, 1.73 mmol)and urea (1.04 g, 17.3 mmol) was heated to 180° C. for 1 h, then cooledto RT. The solid was then suspended in a mixture of EtOAc and water andthen it was filtered and the collected solid was washed with waterseveral times, then air-dried. This intermediate quinazolinone was thensuspended in phosphorus oxychloride (3.0 mL, 32.2 mmol) and then heatedto 100° C. for 1 h. After cooling to RT, the mixture was added dropwiseto an ice-water mixture. The mixture was stirred for 5 minutes and thenthe product was extracted into EtOAc (3×). The combined extracts weredried over anhydrous magnesium sulfate, filtered, and concentrated invacuo to give an oil that was purified by silica gel chromatography togive 2,7-dichloro-6-fluoroquinazoline as a white solid (46 mg, 12%yield). m/z=217 (M+1).

Step 5.4-(3-(1-(7-chloro-6-fluoroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

A mixture of 2,7-dichloro-6-fluoroquinazoline (46 mg, 0.21 mmol),4-(3-(azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetris(2,2,2-trifluoroacetate) (0.15 g, 0.23 mmol), and potassiumcarbonate (0.15 g, 1.06 mmol) in DMSO (1 mL) was heated to 100° C. for 1h, then cooled to RT. Water was added, then the product was extractedinto EtOAc. The combined extracts were washed with water (2×), driedover anhydrous magnesium sulfate, filtered, and concentrated in vacuo togive an oil. This oil was purified by silica gel chromtography to give4-(3-(1-(7-Chloro-6-fluoroquinazolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamideas a light yellow solid (69 mg, 70% yield). m/z=467 (M+1). ¹H NMR (400MHz, chloroFORM-d) δ ppm 3.09 (d, J=4.70 Hz, 3 H) 4.28-4.38 (m, 1 H)4.45-4.54 (m, 4 H) 6.80 (br. s., 1 H) 7.32-7.42 (m, 3 H) 7.71 (d, J=6.65Hz, 1 H) 8.27 (t, J=7.92 Hz, 1 H) 8.58 (d, J=1.76 Hz, 1 H) 8.65 (s, 1 H)8.94 (s, 1 H).

Example 132-fluoro-4-(3-(1-(6-fluoroquinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)-N-methylbenzamide

The title compound was prepared analogously to Example 8 by using2-chloro-6-fluoroquinoline (Combi-blocks) in Step 3. ¹H NMR (400 MHz,chloroFORM-d) δ ppm 3.09 (dd, J=4.79, 0.68 Hz, 3 H) 4.20-4.56 (m, 5 H)6.65 (d, J=9.00 Hz, 1 H) 6.80 (d, J=6.65 Hz, 1 H) 7.21-7.33 (m, 2 H)7.36 (dd, J=12.32, 1.57 Hz, 1 H) 7.42 (dd, J=8.12, 1.66 Hz, 1 H) 7.70(dd, J=9.10, 5.18 Hz, 1 H) 7.83 (d, J=8.80 Hz, 1 H) 8.28 (t, J=8.02 Hz,1 H) 8.56 (d, J=2.35 Hz, 1 H) 8.64 (d, J=2.35 Hz, 1 H). m/z=432 (M+1).

Example 144-(3-(1-(7-chloro-1,5-naphthyridin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

Step 1. (E)-methyl 3-(3-amino-5-chloropyridin-2-yl)acrylate

A solution of 3-amino-2-bromo-5-chloropyridine (2.257 ml, 19.96 mmol),Reactant 2 (0.283 g, 0.399 mmol), triethylamine (3.03 g, 29.9 mmol) andmethyl acrylate (3.44 g, 39.9 mmol) in 5 mL of DMF was heated at 145° C.under microwave irradiation for 35 min. The reaction mixture wasevaporated to dryness and was loaded to flash column (DCM toDCM/EA=10:1) to give 1.98 g of pure (E)-methyl3-(3-amino-5-chloropyridin-2-yl)acrylate (2.7 g, 12.70 mmol, 63.6%yield) as a light yellow solid and 820 mg of less pure product. ¹H NMR(400 MHz, chloroFORM-d) δ ppm=8.01 (d, J=1.8 Hz, 1 H), 7.72 (d, J=15.1Hz, 1 H), 7.01 (d, J=2.0 Hz, 1 H), 6.92 (d, J=15.3 Hz, 1 H), 4.02 (br.s., 2 H), 3.81 (s, 3 H).

Steps 2 & 3. 2,7-dichloro-1,5-naphthyridine

A suspension of (E)-methyl 3-(3-amino-5-chloropyridin-2-yl)acrylate (1.2g, 5.64 mmol) and sodium methoxide (0.786 ml, 14.11 mmol) in 20 mL ofethanol was refluxed for 3 h until the starting material disappeared.The reaction mixture was evaporated to dryness to give crude product7-chloro-1,5-naphthyridin-2(1H)-one. To the crude residue was addedphosphorus oxychloride (5.17 ml, 56.4 mmol) and the resulting mixturewas stirred at 70° C. for 4 h. The excess POCl₃ was removed underreduced pressure and the residue was directly submitted to flash column(DCM) to give 2,7-dichloro-1,5-naphthyridine (540 mg, 2.71 mmol, 48.1%yield) as an off-white solid. ¹H NMR (400 MHz, chloroFORM-d) δ ppm=8.90(d, J=2.2 Hz, 1 H), 8.35 (d, J=8.8 Hz, 1 H), 8.31 (d, J=1.8 Hz, 1 H),7.63 (d, J=8.8 Hz, 1 H). m/z=199 (M+1).

Step 4.4-(3-(1-(7-chloro-1,5-naphthyridin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide

A mixture of4-(3-(azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamidetetrakis(2,2,2-trifluoroacetate) (160 mg, 0.216 mmol),2,7-dichloro-1,5-naphthyridine (47.2 mg, 0.237 mmol), cesium carbonate(86 μl, 1.078 mmol) and bis(tri-tert-butylphosphine)palladium (0) (3.30mg, 6.47 μmol) in 1 mL of dioxane was degassed by bubbling N₂ for 5 min.The reaction mixture was sealed and heated in 100° C. oil bath for 1 h.The reaction mixture was loaded onto flash column (DCM to EA toEA/MeOH=100:2) to give4-(3-(1-(7-chloro-1,5-naphthyridin-2-yl)azetidin-3-yl)pyrazin-2-yl)-2-fluoro-N-methylbenzamide(70 mg, 0.156 mmol, 72.4% yield) as a light yellow solid. ¹H NMR (400MHz, chloroFORM-d) δ ppm=8.65 (d, J=2.3 Hz, 1 H), 8.59 (d, J=2.2 Hz, 1H), 8.52 (d, J=2.2 Hz, 1 H), 8.28 (t, J=8.0 Hz, 1 H), 8.05 (d, J=9.2 Hz,1 H), 8.01 (br. s., 1 H), 7.47-7.32 (m, 2 H), 6.88-6.81 (m, 1 H), 6.80(d, J=9.2 Hz, 1 H), 4.56-4.43 (m, 4 H), 4.43-4.33 (m, 1 H), 3.09 (d,J=4.3 Hz, 3 H). m/z=449 (M+1).

BIOLOGICAL EXAMPLES

The worldwide market for therapies for CNS disorders is worth more than$50 billion and is set to grow substantially in the years ahead. This isbecause: 1) the incidence of many CNS disorders (e.g., Alzheimer'sdisease, stroke, and Parkinson's disease) increase exponentially afterage 65 and 2) the number of people in the world over 65 is about toincrease sharply due to a marked rise in fertility after World War II.However, CNS research and development are associated with significantchallenges: it takes longer to get a CNS drug to market (12-16 years)compared with a non-CNS drug (10-12 years) and there is a higherattrition rate for CNS drug candidates than for non-CNS drug candidates.This is attributable to a variety of factors, including the complexityof the brain, the requirement of CNS drugs to cross the blood-brainbarrier (BBB), and the liability of CNS drugs to cause CNS side effects.The compounds of the invention may be modified by appending appropriatefunctionalities to enhance selective biological properties, such as BBBpenetration, along with pharmacokinetics and drug metabolism, in theprocess of the discovery and development of safe and effective medicinesfor CNS disorders.

Surprisingly, the compounds of the present invention exhibit improvedpharmacokinetics and pharmacodynamics, which relate, directly andindirectly, to the ability of the compound to be effective for itsintended use. For example, the compounds have been surprisingly found topossess improved receptor occupancy (ex vivo RO) coupled with improvedselectivity against PDE2A as shown in Table 1 in terms of IC₅₀ (μM). Inaddition, because the compounds of the invention also possess desirableclearance and permeability/efflux properties, they readily lendthemselves to prodicting in vivo PK and PD properties, which in turnassist in projection of therapeutic target coverage and efficaciousdosages via in vivo absorption, distribution, metabolism and excretionproperties. Increased biological penetration into a given biologicalcompartment (e.g., blood, lymphatic system, central nervous system),increased oral availability, increased solubility, and alteredclearance, metabolism and/or rate of excretion are important factors fordetermining which compounds may be useful drugs and which may not.

TABLE 1 Ex vivo RO rat MDR1 ^(A)10 mpk 1 h Average efflux human MDR1 Ex.PDE10A PDE2A ^(B) 10 mpk 4 h Permeability ratio in efflux ratio in No.(μM) (μM) ^(C) 3 mpk 4 h LLC-PK1 LLC-PK1 LLC-PK1 1 0.0287 10  79% +/−7.8% ^(B) 16.0 2.3 2.9 58.8% +/− 13.5% ^(C) 2 0.0063 10  112% +/− 4.3%^(B)  28.2 2.7 2.4 72%+/12.4% ^(C) 3 0.0031 10 97.4% +/− 10.7% ^(C) 43.62.1 2 4 0.0028 10 93.3% +/− 10% ^(C)   26.5 2.2 3.4 5 0.0075 10 68.3%+/− 15% ^(C)   24.9 2.3 2.5 6 0.0076 10 85.4% +/− 22.3% ^(A) 38.8 1.21.8 62.6% +/− 11.0% ^(C) 7 0.004 10 93.2% +/− 8.6% ^(A)  32.6 3.1 2.95109.8% +/− 12.4% ^(C)  8 0.0005 10  134% +/− 5.3% ^(A)  33.1 2.5 2.883.5% ± 7.2% ^(C)  9 0.0309 10 123.4% +/− 10.8% ^(A)  39.7 2.7 1.8 87.1%+/− 7.1% ^(B)  61.8% +/− 19.3% ^(C) 10 0.0059 7.375 100.6% +/− 13.1%^(A)  39.5 1.2 1.8  108% +/− 8.0% ^(C)  11 0.0166 10   80% +/− 12.0%^(B) 44.5 1.2 1.75 67.5% +/− 8.3% ^(C)  12 0.0039 10 91.4% +/− 15.1%^(C) 37.7 2.8 1.85 13 0.0017 10  77% +/− 8.4% ^(C) 38.0 2.7 3.025 140.0036 10 78.5% +/− 8.3% ^(C)  52.1 1.1 1.25 15 0.0013 10 47.7% +/−11.6% ^(A) 22.7 3.1 10.4 16 0.0026 3.304 52.3% +/− 38.3% ^(A) 49.1 1.21.9 17 0.0020 2.163 72% ± 23% ^(A) 36.6 76 41

The above biological activity data were obtained by using the followingassays of Examples A, B, F and G. Compounds 15, 16, and 17 have thefollowing structures, respectively:

and are named:4-(3-(1-(2-quinolinyl)-3-azetidinyl)-2-pyrazinyl)benzamide;2-fluoro-4-(3-(1-(quinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)benzamide;andN-methyl-3-(3-(1-(quinolin-2-yl)azetidin-3-yl)pyrazin-2-yl)benzamide,respectively.

Example A PDE10A Enzyme Activity and Inhibition

Enzyme Activity

An IMAP TR-FRET assay was used to analyze the enzyme activity (MolecularDevices Corp., Sunnyvale Calif.). 10 μL of serial diluted PDE10A (BPSBioscience, San Diego, Calif.) or tissue homogenate was incubated withequal volumes of diluted fluorescein labeled cAMP or cGMP for 90 min in384-well Polypropylene assay plates (Greiner, Monroe, N.C.) at roomtemperature. After incubation, the reaction was stopped by adding 55 μLof diluted binding reagents and was incubated for 4 hours to overnightat room temperature. The plates were read on an Envision (Perkin Elmer,Waltham, Mass.) for time resolved fluorescence resonance energytransfer. The data were analyzed with Genedata Screener® (Lexington,Mass.).

Enzyme Inhibition.

To check the inhibition profile, 0.2 μL of serial diluted compounds wereincubated with 10 μL of diluted PDE10 enzyme (BPS Bioscience, San Diego,Calif.) or tissue homogenate in a 384-well Polypropylene assay plate(Greiner, Monroe, N.C.) for 60 min at room temperature. Afterincubation, 10 μL of diluted fluorescein labeled cAMP or cGMP substratewas added and incubated for 90 min at room temperature. The reaction wasstopped by adding 55 μL of diluted binding reagents and plates were readon an Envision (Perkin Elmer, Waltham, Mass.) for time resolvedfluorescence resonance energy transfer. The data were analyzed withGenedata Screener® (Lexington, Mass.).

Example B PDE IMAP Assay Protocol

Purified human PDE2A1 and PDE10A2 enzymes were obtained from BPSBioscience (San Diego, Calif.). IMAP™ TR-FRET progressive bindingsystem, FAM-cAMP substrate were from Molecular Devices (Sunnyvale,Calif.).

The PDE IMAP assay was conducted in a 384-well black Greinerpolypropylene plate (Sigma, St. Louis, Mo.). PDE inhibitors were serialdiluted in 100% DMSO and dispensed into assay plate at 200 nL per wellusing Echo® Liquid Handling System from LABCYTE. Ten μL of PDE enzyme inIMAP reaction buffer (10 mM Tris-HCl, pH 7.2, 10 mM MgCl₂, 0.05% NaN₃,and 0.01% Tween-20) was added into the assay wells. The PDE enzymeconcentration used was based on each lot of enzyme activity, to ensureenzyme reaction falls in a linear range under assay condition. 1.4 nM ofPDE2 or 8 pM PDE10 were used in the assay system. Enzyme waspre-incubated with inhibitors for 60 minutes at room temperature beforeaddition of 10 uL of substrate addition, which results in 100 nM ofFAM-cAMP in the reaction. Enzyme reaction was allowed to proceed at roomtemperature for 90 min, and the reaction is stopped by 55 μl addition ofbinding reagent according to manufacturer's recommendation. The mixtureis further incubated at room temperature for additional 4 hours, andsignal was read on an Envision multimode reader (PerkinElmer).Fluorescence signals were measured at 520 nm and 485 nm. The signalratio at 520/485 nm corresponded to the generation of reaction productof AMP, and it was used in all data analysis. Values from DMSO-treatedwells were normalized to POC=100, and no-enzyme wells were normalized toPOC=0. IC₅₀ values were determined by using the Genedata ScreenerV9.0.1. The curve fitting algorithm used for dose response data analysisin Genedata Screener is a custom implementation of a robustcurve-fitting algorithm called ROUT (Robust regression with outlierdetection) and uses a four-parameter logistical (4PL) Hill model.

Example C Apomorphine Induced Deficits in Prepulse Inhibition of theStartle Response in Rats, an In Vivo Test for Antipsychotic Activity

The thought disorders that are characteristic of schizophrenia mayresult from an inability to filter, or gate, sensorimotor information.The ability to gate sensorimotor information can be tested in manyanimals as well as in humans. A test that is commonly used is thereversal of apomorphine-induced deficits in the prepulse inhibition ofthe startle response. The startle response is a reflex to a suddenintense stimulus such as a burst of noise. In this example, rats can beexposed to a sudden burst of noise, at a level of 120 db for 40 msec,e.g., the reflex activity of the rats can be measured. The reflex of therats to the burst of noise may be attenuated by preceding the startlestimulus with a stimulus of lower intensity, at 3 db to 12 db abovebackground (65 db), which attenuates the startle reflex by 20% to 80%.

The prepulse inhibition of the startle reflex, described above, may beattenuated by drugs that affect receptor signaling pathways in the CNS.One commonly used drug is the dopamine receptor agonist apomorphine.Administration of apomorphine reduces the inhibition of the startlereflex produced by the prepulse. Antipsychotic drugs such as haloperidolprevents apomorphine from reducing the prepulse inhibition of thestartle reflex. This assay can be used to test the antipsychoticefficacy of PDE10 inhibitors, as they reduce the apomorphine-induceddeficit in the prepulse inhibition of startle.

Example D Conditioned Avoidance Responding (CAR) in Rats, an In VivoTest for Antipsychotic Activity

Conditioned avoidance responding (CAR) occurs, for instance, when ananimal learns that a tone and light predict the onset of a mild footshock. The subject learns that when the tone and light are on, it mustleave the chamber and enter a safe area. All known antipsychotic drugsreduce this avoidance response at doses which do not cause sedation.Examining the ability of test compounds to suppress the conditionedavoidance has been widely used for close to fifty years to screen fordrugs with useful antipsychotic properties.

In this example, an animal can be placed in a two-chambered shuttle boxand presented with a neutral conditioned stimulus (CS) consisting of alight and tone, followed by an aversive unconditioned stimulus (US)consisting of a mild foot shock through a floor grid in the shuttle boxchamber. The animal can be free to escape the US by running from onechamber to the other, where the grid is not electrified. After severalpresentations of the CS-US pair, the animal typically learns to leavethe chamber during the presentation of the CS and avoid the USaltogether. Animals treated with clinically-relevant doses ofantipsychotic drugs have a suppression of their rate of avoidances inthe presence of the CS even though their escape response to the shockitself is unaffected.

Specifically, conditioned avoidance training can be conducted using ashuttle box (Med Associates, St. Albans, Vt.). The shuttle box istypically divided into 2 equal compartments that each contain a lightsource, a speaker that emits an 85 dB tone when activated and anelectrified grid that can deliver a scrambled foot shock. Sessions canconsist of 20 trials per day (intertrial interval of 25-40 sec) duringwhich a 10 sec illumination and a concurrent 10 sec tone signals thesubsequent delivery of a 0.5 mA shock applied for a maximum of 10 sec.Active avoidance, defined as the crossing into the opposite compartmentduring the 10 sec conditioning stimuli (light and tone) prevents thedelivery of the shock. Crossing over to the other compartment after thedelivery of the shock terminates shock delivery and may be recorded asan escape response. If an animal does not leave the conditioning chamberduring the delivery of the shock it is recorded as an escape failure.Training can be continued daily until the avoidance of 16 or more shocksout of 20 trials (80% avoidance) on 2 consecutive days is achieved.After this criterion is reached the rats may be given one day ofpharmacological testing. On test day, rats can be randomly assigned toexperimental groups, weighed and injected intraperitoneally (i.p.) (1 cctuberculin syringe, 26⅜ gauge needle) or per os (p.o.) (18 gauge feedingneedle) with either control or compound solutions. Compounds can beinjected at 1.0 ml/kg for i.p. and 10 mL/kg for p.o. administration.Compounds can be administered either acutely or chronically. Fortesting, each rat may be placed in the shuttle box, and given 20 trialswith the same parameters as described above for training trials. Thenumber of avoidances, escapes, and escape failures can be recorded.

Example E PCP-induced Hyperactivity (PCP-LMA)

Equipment Used: 4×8 home cage photobeam activity system (PAS) frame fromSan Diego Instruments. Open PAS program and prepare an experimentalsession using the following variables:

Multiphase experiment

300 sec/interval (5 min)

12 intervals (1 h)

Individual on screen switches.

Start recording after first beam break.

End session after end of interval.

Cage Preparation:

Techniplast™ rat cage with filter top, but no wire lid. Place ˜400 mLbedding and one food pellet in cage and place 250 mL techniplast waterbottle in holder on filter top. Place the prepped cage in the PAS frame.Make sure bedding or pellet doesn't block the photobeams.

Animal Preparation:

Mark rats and record their weights. Bring rats to testing room.

Phase I: Habituation

Start the experiment session. Place the rat in the enclosure. Thecomputer should start recording when it detects the rat breaking thebeam. The computer will record for 1 h. During the habituation phase,prepare risperidone (positive control): Measure out risperidone,calculate final volume at 1 mg/mL concentration and add 1% glacialacetic acid of the final volume to dissolve risperidone. Whenrisperidone is dissolved, add saline to final volume to make aconcentration of 1 mg/mL. Fill syringes (3 mL syringes with 23 g ½needle or oral gavage needle) with Amgen compound solution (5 mL/kg) orrisperidone (1 mL syringe with 23 g ½ needle) control (1 mL/kg) s.c.

Phase II: Compound Pre-Treatment

Make sure Phase I has ended. Remove rat from enclosure, start the nextphase using on-screen individual switch, administer compound p.o or i.p.and control s.c. and place rat back in the enclosure. The computershould start recording when it detects the rat breaking the beam. Thecomputer will record for 1 h.

During phase II, prepare pcp: Dissolve pcp in saline to a concentrationof 5 mg/mL.

Fill syringes (1 mL syringes with 26 g ⅜ needle) with pcp solution (1mL/kg).

Phase III: PCP Administration.

Make sure phase II is ended. Remove rat from enclosure, start the nextphase using on-screen individual switch, administer pcp s.c. and placerat back in the enclosure. The computer will record for 1 h.

Clean-Up:

End-session to terminate experiment and so that computer will compiledata. Export raw data to spreadsheet file for data analysis. Euthanizerats and take necessary tissue/sample for PK.

Data Generation:

Export raw data to spreadsheet file for data analysis. Total time ofmovement is recorded as the number of photobeam breaks by the computer.Total time of movement (seconds) is combined into 5 minute bins andaveraged for each treatment group for an N of 7-10 animals. Data areanalyzed for statistical significance using a two-way ANOVA followed bya Bonferroni's post-hoc test for multiple comparisons.

Example F PDE10 Ex Vivo Receptor Occupancy (RO) Screening Protocol

The ex vivo screening protocol was approved by Amgen's InstitutionalAnimal Care and Use Committee (IACUC) and in accordance with theNational Institutes of Health Guide for Care and Use of LaboratoryAnimals in facilities accredited by the Association for the Assessmentand Accreditation of Laboratory Animal Care (AALAC).

PDE10 inhibitors were dissolved in 2% Hydroxypropylmethylcellulose(HPMC), 1% Tween-80, pH 2.2 with methanesulfonic acid. Male SpragueDawley® rats weighing 180-225 g (4 per group) were dosed orally witheither vehicle or PDE10 inhibitors (3 mg/kg or 10 mg/kg) and thenreturned to their home cage to allow for absorption of the compounds.After one hour (with 10 mg/kg PDE10 inhibitor) or four hours (with 3mg/kg or 10 mg/kg PDE10 inhibitor) rats were sacrificed by CO₂inhalation. Blood was obtained by heart puncture and plasma was frozenand stored at −80° C. for exposure analysis. Brains were removed andimmediately frozen in chilled methylbutane, and stored at −80° C. untilcutting. Three coronal brain slices per brain containing the striatumwere cut at 20 mm using a cryostat and placed onto microscope slides,air-dried and stored at −20° C. For radioligand binding experiments,slides were thawed at room temperature and then incubated with 1 nM atritium labeled tracer compound (insert citation) in binding buffer (150mM Phosphate-buffered saline containing 2 mM MgCl₂ and 100 mM DTT, pH7.4) for 1 minute at 4° C. To assess non-specific binding, slidescontaining adjacent brain sections were incubated in the same solutionwith addition of 10 mM of an unlabelled, structurally unrelated PDE10antagonist. Afterwards slides were washed 3 times in ice-cold bindingbuffer, dipped into distilled water to remove buffer salts, and driedunder a stream of cold air. Emission of beta particles from the sectionswas counted for 8 hours in a Beta Imager 2000 (Biospace, Paris, France)and digitized and analyzed using M3 Vision software (Biospace, Paris,France). Total binding radioactivity in the striatum was measured ascpm/mm² in hand-drawn regions of interest and averaged across the threesections per brain. Non-specific binding was subtracted to obtainspecific binding values and percent occupancy was calculated by settingvehicle specific binding as 0% occupancy.

Example G Permeability and Transcellular Transport Protocol Materials

Digoxin and mannitol were purchased from Sigma-Aldrich (St. Louis, Mo.).3H-digoxin and 14C-mannitol were purchased from PerkinElmer Life andAnalytical Sciences (Boston, Mass.). Transport buffer was prepared usingHank's balanced salt solution (HBSS) supplemented with 10 mM Hepes, pH7.4 and 0.1% BSA (HHBSS, Invitrogen, Grand Island, N.Y., BSA, BovineSerum Albumin, Calbiochem, La Jolla, Calif.).

Cell Lines and Cell Cultures.

Cultures were incubated at 37° C. in a humidified (95% relativehumidity) atmosphere of 5% CO2/95% air. The parental cell line LLC-PK1(porcine renal epithelial cells) was purchased from American TypeCulture Collection (ATCC, Manassas, Va.). Human MDR1 and Sprague-Dawleyrat mdra1 transfectants in LLC-PK1 were generated at Amgen (ThousandOaks, Calif.). Cells were cultured in Medium 199 supplemented with 2 mML-glutamine, penicillin (50 units/mL), streptomycin (50 μg/mL), and 10%(v/v) fetal bovine serum (all from Invitrogen) (Schinkel et al, 1995).

Permeability and Transcellular Transport of Test Compounds

LLC-PK1, MDR1-LLC-PK1, and mdrla-LLC-PK1 cell monolayers were seededonto porous (1.0 μm) polycarbonate 96-well transwell membrane filters(Millipore Corp., Billerica, Mass.) and cultured for six days with onemedia replacement on day four prior to transwell experiments. Cells werewashed once with warmed HHBS prior to transwell experiments. Experimentswere initiated by replacing the buffer in each compartment with 0.15 mLof HBSS containing 0.1% BSA with and without 5 μM of test compound intriplicate wells. The plates were incubated for two hours at 37° C. inan EVO incubator with shaking. Aliquots (100 μl) from both donor andreceiver chambers were transferred to 96 well plates or scintillationvials. Protein was precipitated by addition of 200 μL acetonitrilecontaining 0.1% formic acid and prazosin (25 ng/mL) as internalstandard. After vortexing and centrifugation at 3000 rpm for 20 min, 150μL supernatant samples were transferred to a new plate containing 50 μLwater for LC-MS/MS analysis. Transcellular transport of 3H-Digoxin wasused as a positive control for Pgp. Paracellular permeability of14C-Mannitol was used to measure the integrity of the monolayer. Sampleradioactivity was measured using a liquid scintillation counter (PackardTri-Carb 2910TR, PerkinElmer).

The apparent permeability coefficient (Papp) of all tested agents wasestimated from the slope of cumulative amount (dQ) of the agent vs. time(dt), and the equation:Papp=(dQ/dt)/(A*C0)

where dQ/dt is the penetration rate of the agent (μm/s), A is thesurface area of the cell layer on the Transwell (0.11 cm2), and C0 isthe initial concentration of the test compound (μM).

The foregoing is merely illustrative of the invention and is notintended to limit the invention to the disclosed compounds. Variationsand changes which are obvious to one skilled in the art are intended tobe within the scope and nature of the invention which are defined in theappended claims. All patents, patent applications, and otherpublications recited herein are hereby incorporated by reference intheir entirety.

What is claimed is:
 1. A compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein: X¹ is N or CR⁴;X² is N or CR⁵; wherein 0 to 1 of X¹ and X² are N; each of p and q isindependently; wherein the sum of p and q is 4; and each R¹, R², R³, R⁴,and R⁵ is independently hydrogen or halo.
 2. The compound according toclaim 1, or a pharmaceutically acceptable salt thereof, wherein X¹ is Nand X² is CH.
 3. The compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein X¹ is CH and X² is N.4. The compound according to claim 1, or a pharmaceutically acceptablesalt thereof, wherein X¹ is CH and X² is CH.
 5. The compound accordingto claim 1, or a pharmaceutically acceptable salt thereof, wherein R² isfluoro.
 6. A compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein: X¹ is N or CR⁴;X² is N or CR⁵; wherein 0 to 1 of X¹ and X² are N; each of p and q isindependently 2; wherein the sum of p and q is 4; and each R¹, R², R³,R⁴, and R⁵ is independently hydrogen or halo; wherein one of R¹, R², andR³ is hydrogen.
 7. The compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein two of R¹, R², and R³are hydrogens.
 8. The compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein R¹, R², and R³ arehydrogen.
 9. The compound according to claim 1, or a pharmaceuticallyacceptable salt thereof, wherein one of R¹ and R² is fluoro.
 10. Thecompound according to claim 1, or a pharmaceutically acceptable saltthereof, wherein one of R¹ and R² is chloro.
 11. The compound accordingto claim 1, or a pharmaceutically acceptable salt thereof, wherein R¹ isfluoro or chloro.
 12. The compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein R¹ is hydrogen and R²is chloro or fluoro.
 13. The compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein R¹ is chloro or fluoroand R² is hydrogen.
 14. The compound according to claim 1, or apharmaceutically acceptable salt thereof, which is: Ex. Structure 1

2

3

4

5


15. A pharmaceutical composition comprising a compound according toclaim 1, or a pharmaceutically acceptable salt thereof, and apharmaceutically acceptable excipient.
 16. A method of treating adisorder that may be treated with PDE10 inhibitors comprising the stepof administering to a patient in need thereof a therapeuticallyeffective amount of a compound according to claim 1, or apharmaceutically acceptable salt thereof, wherein said disorder isschizophrenia.
 17. A method of treating a disorder that may be treatedwith PDE10 inhibitors according to claim 16, and in combination with asuitable schizophrenia drug.
 18. A method of preparing a compoundFormula (I) according to claim 1; comprising the step of: (a) reacting acompound of formula 3 with a compound of formula 5:

wherein X¹, X², R¹, R², R³, p and q are as defined in the compound offormula (I); and wherein LG₁ is a leaving group and M is a metal moiety;in the presence of a solvent and a catalyst; or (b) reacting a compoundof formula 2 with a compound of formula 4:

wherein X¹, X², R¹, R², R³, p and q are as defined in the compound offormula (I), and LG₂ is a leaving group; in the presence of a solventand a base; to prepare the compound of formula (I).